04sql and advanced sql

8/6/2019 04SQL and Advanced SQL

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IBM DB2 Universal Databases 8.1

SQL & Advanced SQL

Chapter - 4

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SQL & Advanced SQL1. SQL

1. SQL Getting Started

2. Database Objects

3. Data Types, Constraints, Rules4. Data Definition Language

5. Data Manipulation Language

6. Indexes

7. Views

8. Identity Column

2. Advanced SQL1. User Defined Data Types

2. Sequences

3. Advanced Functions

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SQL1. SQL Getting Started

2. Database Objects

3. Data Types

4. Data Definition Language, Constraints & Rules


6. Indexes

7. Views

8. Identity Columns

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Standard language of relational database access is SQL(Structured Query Language).

Designed for accessing tabular data.

Three major categories..

DDL (Data Definition Language) - Used to create, modify, or drop database

objects

DML (Data Manipulation Language) - Used to select, insert, update, or delete

database data (records)

DCL (Data Control Language) - Used to provide data object access control

What is SQL ?

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Data Types

Each column in DB2 table must be associated with a data type.The data type indicates kind of data that is valid for column.

There are two major categories of data types in DB2...

Built-in data types

User-defined data types

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User-Defined Data Types

User-defined distinct type:To create a new data type that has its own semantics based on existing built-in

data types.

User-defined structured type:

To create a structure that contains sequence of named attributes each of which

has a data type.

Is an extension of DB2 Object Relational functions

User-defined reference type:

Is a companion type to a user-defined structured type

Is a scalar type that shares a common representation with one of the built-in

data types.

May be used to reference rows in another table that uses a user-defined

structured type.

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2. Database Objects

3. Data Types



6. Indexes

7. Views

8. Identity Columns

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Tables

Is an unordered set of rows.Rows consist of columns.

Each column is based on a data type.

There are three types of tables:

Permanent (base) tables

Temporary (declared) tables

Temporary (derived) tables

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Schema

Schemas are database objects used in DB2 to logically group otherdatabase objects.

Most database objects are named using a two-part naming

convention (SCHEMA_NAME.OBJECT_NAME ).

When an object is created without specifying a schema, object will

be associated with an implicit schema using the authorization ID.

When an object is referenced in an SQL statement, it is also

implicitly qualified with authorization ID of issuer (dynamic

SQL) if no schema name is specified in SQL statement.

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The CURRENT SCHEMA special register contains defaultqualifier to be used for unqualified objects referenced for dynamic

SQL statements issued from within a specific DB2 connection.

Value can be modified by user with SET CURRENT SCHEMA

statement.

Can use the QUALIFIER option of BIND command to define

default qualifier at bind time.

NOTE: for temporary tables 'session' qualifier is used

Schema

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Tablespaces

Logical layers between database and tables stored in that database.

Table spaces are created within a database, and tables are created

within table spaces.

DB2 supports two kinds of table spaces:

System Managed Space (SMS)

Database Managed Space (DMS)

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Views

Virtual tables derived from one or more tables or viewsCan be used interchangeably with tables when retrieving data.

When changes are made to data through a view, the data is

changed in underlying table itself.

Views do not contain real data.

Created to limit access to sensitive data while allowing more

general access to other data.

Can be deletable, updatable, insertable, and read-only.

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Can be created on computed columns ...So that optimizer can save computation time by using index instead of doing

calculations.

Indexes are maintained automatically by DB2 as data is inserted,

updated, and deleted.

Indexes

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Indexes

Can be defined ...

In ascending or descending order,

Is unique or nonunique, and

On a single column or multiple columns,

To support both forward and reverse scans.

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Buffer Pools

Are database objects used to cache data pages in memory.

Once a data page is placed in a buffer pool, physical I/O access to

disk can be avoided.

Buffer pools can be assigned to cache only a particular table space,

if required.

Every database will have atleast one bufferpool

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Transactions

Is a sequence of SQL statements that execute as a single operation.

Term 'unit of work' is synonymous with the term 'transaction'.

Starts implicitly with first executable SQL statement in a program.

Ends when either an explicit or implicit COMMIT or ROLLBACK

statement is encountered.

SAVEPOINTs are like the bookmarks in a transaction, used to

control the scope of ROLLBACK statement. SAVEPOINT does

not end the current transaction.

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2. Database Objects

3. Data Types



6. Indexes

7. Views

8. Identity Columns

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Data Types

Categories of DB2 supplied datatypes:Numeric

String (Binary, Single Byte, Double Byte)

Datetime

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Numeric Data Types

DB2 data types that can be used to store numeric data are:

SMALLINT

INTEGER

BIGINT

DECIMAL/NUMERIC

REAL

DOUBLE

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Small Integer (SMALLINT)

Uses least amount of storage in database for each value.

Data value range for a SMALLINT is -32768 to 32767.

Precision for a SMALLINT is 5 digits (to the left of the

decimal).

Two bytes of database storage are used for each

SMALLINT column value.

Numeric Data Types

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Integer (INTEGER)

Takes twice as much storage as a SMALLINT but has a

greater range of possible values.

Range value for INTEGER data type is -2,147,483,648 to

2,147,483,647 .

Precision for INTEGER is 10 digits to the left of the

decimal.

Four bytes of database storage are used for each

INTEGER column value.

Numeric Data Types

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Big Integer (BIGINT)

Is available for supporting 64-bit integers.

Range is -9,223,372,036,854,775,808 to

+9,223,372,036,854,775,807 .

Eight bytes of database storage are used for each BIGINT

column value.

NOTE:As platforms include native support for 64 bit integers, processing of large

numbers with BIGINT is more efficient than processing with DECIMAL and

more precise than DOUBLE or REAL .

Numeric Data Types

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Decimal (DECIMAL/NUMERIC)

Is used for numbers with fractional and whole parts.

DECIMAL data is stored in a packed format.

Precision and scale must be provided

NOTE:

The precision is the total number of digits (range from 1 to 31), and the scale is

the

Number of digits in the fractional part of the number.

Numeric Data Types

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Decimal (DECIMAL/NUMERIC):

Terms NUMERIC,NUM,DECIMAL, and DEC can all be

used to declare a decimal/numeric column.

If a decimal data type is to be used in a C program, host

variable must be declared as a double.

NOTE:

A DECIMAL number takes up p/2 + 1 bytes of storage, where p is the

precision used.

For example, DEC(8,2) would take up 5 bytes of storage (8/2 + 1), whereasDEC(7,2) would take up only 4 bytes (truncate the division of p/2).

Numeric Data Types

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Single-Precision Floating-Point (REAL/FLOAT):A REAL data type is an approximation of a number.

Approximation requires 32 bits / 4 bytes of storage.

To specify single-precision number using REAL

datatype,its length must be defined between 1 and 24

Double-Precision Floating-Point (DOUBLE/FLOAT)

DOUBLE/ FLOAT data type is an approximation of a

number.

Approximation requires 64 bits or 8 bytes of storage.

To specify double-precision number using FLOAT data

type, its length must be defined between 25 and 53.

Note:

Exponential notation is used to represent REAL ,DOUBLE, and FLOAT data

values.

Numeric Data Types

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String Data Types

Fixed-Length Character String (CHAR)Strings are stored in database using entire defined amount

of storage.

Length of a fixed-length string must be between 1 and 254

characters.

If value for length is not specified, a value of 1 is

assumed.

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Varying-Length Character String (VARCHAR)Strings are stored using only amount of space required to

store data.

Term CHAR VARYING or CHARACTER VARYING

can be used

Maximum length of VARCHAR column is 32,672 bytes.

String Data Types

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Varying-Length Long Character Strings (LONG VARCHAR) :

Used to store character data with a varying length.

Maximum length of a LONG VARCHAR column is

32,700.

Notes:

LONG VARCHAR data types are similar to CLOB data types.

The FOR BIT DATA clause can be used following character string column

definition. During data exchange, data is treated and compared as binary (bit)

data.

String Data Types

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Character Large Object (CLOB)

Are varying-length SBCS (single-byte character set) or

MBCS (multibyte character set) character strings.

Used to store greater than 32KB of text.

Maximum size for each CLOB column is 2GB

(gigabytes).

String Data Types

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Double-Byte Character Strings (GRAPHIC):GRAPHIC data types represent a single character using 2

bytes of storage.

The GRAPHIC data types include:

GRAPHIC (fixed length - maximum 127 characters)

VARGRAPHIC (varying length - maximum 16336

characters)

LONG VARGRAPHIC (varying length - maximum

16350 characters).

String Data Types

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Double-Byte Character Large Objects (DBCLOB)

Are varying-length character strings

Are stored using 2 bytes to represent each character.

Are used for large amounts (>32KB) of double-byte text

data such as Japanese text.

String Data Types

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Binary Large Object (BLOB)

Are variable-length binary strings.

Data is stored in a binary format .

Is useful for storing nontraditional relational database

information (audio, video).

Maximum size of each BLOB column is 2GB (gigabytes).

Binary Data Type

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Date and Time Data Types

DATE :

Is stored internally as a (packed) string of 4 bytes.

Externally, string has a length of 10 bytes

(MM-DD-YYYY - can vary and is dependent on country

code).

TIME :


Externally, string has a length of 8 bytes (HH-MM-SS -

this representation may vary).

TIMESTAMP :


Externally, string has a length of 26 bytes

(YYYY-MM-DD-HH-MM-SS-NNNNNN ).

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External File Data Types (DATALINK)

Is an encapsulated value

Contains a logical reference from database to a file stored in

a Data Links Manager Server, which is outside database.

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2. Database Objects

3. Data Types

4. Data Definition Language, Constraints & Rules5. Data Manipulation Language

6. Indexes

7. Views

8. Identity Columns

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Managing Database Objects - DDL

To create, modify, delete objects in a database, SQL Data

Definition Language (DDL) is used.

DDL has four basic SQL statements:

CREATE

ALTERDROP

DECLARE

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CREATE Statement

Table

Index

Schema

View

User-defined function

User-defined data type

Buffer pool

Stored procedures

Trigger

Alias

Method

Transform

Nickname

Sequence

Table space

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DECLARE Statement

It is used to create temporary tables that are used only during a

session.

The only object that can be DECLARED is a table

DECLARE GLOBAL TEMPORARY TABLE T1 LIKETRANSACTIONS ON COMMIT PRESERVE ROWS NOT

LOGGED IN SESSIONTEMP;

Note:

'LIKE' clause defines a table with same column names, data types andnullability characteristics of each of the columns of specified table.

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DROP Statement

To delete objects from database.

Can drop any object created with CREATE and

DECLARE statements.

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ALTER Statement

Table

Table space

Database partition

Procedure

Function

Nickname

Sequence

Type

View

Method

User mapping

Buffer pool

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Index can not be altered.

It has to be dropped and re-created.

Every time a DDL statement (except for DECLARE statement) is

issued, catalog is updated.

Update includes a creation or modification timestamp and authorization ID ofthe user issuing the statement.

Important...

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Constraints

Three types of constraints:

Unique constraint

Ensures unique values of a key in a table.

Referential integrity

Enforces referential constraints on insert, update, delete

operations.

Are imparted using insert rules, delete rules and update

rules.

Table check constraint

Verifies that changed data does not violate conditions

specified when a table was created or altered.

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INSERT rule is implicit when a foreign key is specified.

A row can be inserted at any time into a parent table without

any action being taken in dependent table.

A row cannot be inserted into dependent table unless there is

a row in parent table with a parent key value equal to foreign

key value of row being inserted, unless foreign key value is

null.

If an INSERT operation fails for one row during an attempt

to insert more than one row, all rows inserted by the

statement are removed from the database.

INSERT Rules

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DELETE Rules

RESTRICT

Prevents any row in parent table from being deleted if any

dependent rows are found.

NO ACTION

Enforces the presence of a parent row for every child after

all the referential constraints are applied.

This is the default.

The difference between NO ACTION and RESTRICT is

based on when constraint is enforced.

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DELETE Rules

CASCADE

Implies that deleting a row in parent table automatically

deletes any related rows in dependent table.

SET NULL

Ensures that deletion of a row in parent table sets values

of foreign key in any dependent row to null (if nullable).

Other parts of row are unchanged.

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UPDATE Rules

RESTRICT

Update for parent key will be rejected if a row in

dependent table matches original values of key.

NO ACTION

Update operation for parent key will be rejected if any

row in dependent table does not have a corresponding

parent key when update statement is completed .

This is the default.

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Table-Check Constraint

Will enforce data integrity at table level.

Once defined for a table, every UPDATE, INSERT statement

will involve checking the constraint.

If constraint is violated, row will not be inserted or updated.

Can be defined at table creation time or later using ALTER

TABLE statement.

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Adding Table-Check Constraint

When a check constraint is added to a table that contains

data, following can happen:

All rows meet check constraint...

Check constraint will be created successfully.

Some or all rows do not meet check constraint...

Check constraint will not be created

ALTER TABLE EMPLOYEE ADD CONSTRAINT

check_job CHECK (JOB IN ('Engineer','Sales','Manager'));

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Create Table Statement

CREATE TABLE Department (Deptnumb SMALLINT NOT

NULL, Deptname VARCHAR(20), Mgrno

SMALLINT,PRIMARY KEY(Deptnumb) )

CREATE TABLE Employee (Id SMALLINT NOT NULL,Name

VARCHAR(9) NOT NULL, Dept SMALLINT,Job CHAR(5) CHECK (Job IN ('Sales','Mgr','Clerk')),

Hiredate DATE WITH DEFAULT CURRENT DATE,

Salary DECIMAL(7,2), Comm DECIMAL(7,2),

CONSTRAINT UNIQUEID PRIMARY KEY(Id),

FOREIGN KEY(Dept) references DEPARTMENT(Deptnumb)ON DELETE RESTRICT) IN HUMRES INDEX IN

HUMRES_IDX NOT LOGGED INITIALLY

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Alter Table Statement

Adding one or more columns to a table

Adding or dropping a primary key

Adding or dropping one or more unique or referential constraints

Adding or dropping one or more check constraint definitions

Altering the length of a VARCHAR column

Altering a reference type column to add a scope

Altering or dropping a partitioning key

Changing table attributes such as the DATA CAPTURE ,

PCTFREE , LOCKSIZE , or APPEND mode option

Activating the not logged initially attribute of the table

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Alter Table Statement

ALTER TABLE Employee ACTIVATE NOT LOGGED

INITIALLY LOCKSIZE TABLE APPEND ON VOLATILE

LOCKSIZE : indicates the granularity of locks

APPEND ON : indicates whether data is appended to end of atable or inserted where free space is available.

VOLATILE : indicates to optimizer that cardinality of table can

vary significantly at run time, from empty to quite large.

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2. Database Objects

3. Data Types


6. Indexes

7. Views

8. Identity Columns

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Data Manipulation Language

Retrieving Data

Inserting Data

Updating Data

Deleting Data

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Retrieving Data

SELECT * FROM EMPLOYEE

SELECT EMPNO, FNAME, LNAME FROM EMPLOYEE

ORDER BY FNAME

SELECT EMPNO, FNAME, LNAME FROM EMPLOYEEWHERE EMPNO = 150

SELECT * FROM EMPLOYEE FETCH FIRST 5 ROWS ONLY

SELECT EMPNO, FNAME, LNAME FROM EMPLOYEE

WHERE MIN(SALARY) < 1000

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Retrieving Data From More Than One Tables -Joins

Process of combining data from two or more tables is achieved

using joins.

Database manager forms all combination of rows from specified

tables.

For each combination it checks the join condition.

Data types of the columns invloved in the join condition do not

have to be identical but they have to be compatible.

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SAMP_PROJECT Table

NAME PROJ

Haas AD3100

Thompson PL2100

Walker MA2112

Lutz MA2111

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SAMP_STAFF Table

NAME JOB

Hass PRES

Thompson MANAGER

Lucchessi SALESREP

Nicholls ANALYST

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SELECT SAMP_PROJECT.NAME, SAMP_PROJECT.PROJ,

SAMP_STAFF.NAME, SAMP_STAFF.JOB FROM

SAMP_PROJECT, SAMP_STAFF

Query With-Out Join Condition

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NAME PROJ NAME JOB

---------- ------ ---------- --------

Haas AD3100 Haas PRES

Thompson PL2100 Haas PRES

Walker MA2112 Haas PRES

Lutz MA2111 Haas PRES

Haas AD3100 Thompson MANAGERThompson PL2100 Thompson MANAGER

Walker MA2112 Thompson MANAGER

Lutz MA2111 Thompson MANAGER

Haas AD3100 Lucchessi SALESREP

Thompson PL2100 Lucchessi SALESREPWalker MA2112 Lucchessi SALESREP

Lutz MA2111 Lucchessi SALESREP

Haas AD3100 Nicholls ANALYST

Thompson PL2100 Nicholls ANALYST

Walker MA2112 Nicholls ANALYST

Lutz MA2111 Nicholls ANALYST

Cartesian / Cross Product

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Main Types of Joins

Inner Join:

Keeps only the rows from the cross product that meet the join condition.If a

row exists in one table, but not the other, the information is not included in the

result table.

Outer Join:

Are a concatenation of the inner join and rows from the left table, right table,

or both tables that are missing from the inner join.

NOTE:

When you perform an outer join on two tables, you arbitrarily assign one table

as the left table and the other one as the right table.

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Types of Outer Joins

Left outer join

Includes the inner join and the rows from the left table that are not included in

the inner join.

Right outer join

Includes the inner join and the rows from the right table that are not included

in the inner join.

Full outer joinIncludes the inner join and the rows from both the left and right tables that are

not included in the inner join.

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Example of Inner Join

The inner join lists full-time employees who are assigned to project :

SELECT SAMP_PROJECT.NAME,

SAMP_PROJECT.PROJ, SAMP_STAFF.NAME, SAMP_STAFF.JOB

FROM SAMP_PROJECT, SAMP_STAFF

WHERE SAMP_STAFF.NAME = SAMP_PROJECT.NAME

OR


SAMP_PROJECT.PROJ, SAMP_STAFF.NAME,SAMP_STAFF.JOB

FROM SAMP_PROJECT INNER JOIN SAMP_STAFF

ONSAMP_STAFF.NAME = SAMP_PROJECT.NAME

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Result of Inner Join Query

The result :

NAME PROJ NAME JOB

---------- ------ ---------- --------


Thompson PL2100 Thompson MANAGER

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Left Outer Join


SAMP_STAFF.NAME, SAMP_STAFF.JOB

FROM SAMP_PROJECT LEFT OUTER JOIN SAMP_STAFF

ON SAMP_PROJECT.NAME = SAMP_STAFF.NAME

The result:

NAME PROJ NAME JOB

---------- -------------------- ---------- --------------------

Haas AD3100 Haas PRESLutz MA2111 - -


Walker MA2112 - -

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Right Outer Join


SAMP_PROJECT.PROJ, SAMP_STAFF.NAME,

SAMP_STAFF.JOB

FROM SAMP_PROJECT RIGHT OUTER JOIN SAMP_STAFF

ON SAMP_PROJECT.NAME = SAMP_STAFF.NAME

The result :

NAME PROJ NAME JOB

---------- -------------------- ---------- --------------------


- - Lucchessi SALESREP

- - Nicholls ANALYST


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Full Outer Join


SAMP_STAFF.NAME, SAMP_STAFF.JOB

FROM SAMP_PROJECT FULL OUTER JOIN SAMP_STAFF

ON SAMP_STAFF.NAME = SAMP_PROJECT.NAME

The result :

NAME PROJ NAME JOB

---------- -------------------- ---------- --------------------


- - Lucchessi SALESREP

- - Nicholls ANALYSTThompson PL2100 Thompson MANAGER

Lutz MA2111 - -

Walker MA2112 - -

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Retrieving Data using - DB2 Functions

Scalar functions

Also known as row functions

Provide a result for each row of the result table. A scalar function can be used

any place an expression is allowed.

Column functions

Also known as vector functions.

Work on a group of rows to provide a result.

The group is specified using a fullselect and optionally grouped using GROUP

BY clause.

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Retrieving Data using - DB2 Functions

Scalar Functions:

SELECT lname, SUBSTR(CHAR(wphone),1,3) FROM db2cert.candidate

SELECT fname, MONTHNAME(date_taken) FROM candidate c, test_taken

tt WHERE c.cid=tt.cid

SELECT empno, sal FROMemployee WHERE UCASE(firstnme) = 'BILL'

Column Functions:SELECT MAX(smallint(length)) FROM test

SELECT AVG(noseats) FROM test_center

SELECT country, AVG(noseats) FROM test_center GROUP BY country

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Searching for String Patterns

SELECT fname,lname,wphone,hphone FROM candidate WHERE

fname LIKE 'G%' ORDER BY lname, fname

SELECT fname,lname,wphone,hphone FROM candidate WHERE

fname LIKE '_a%' ORDER BY lname,fname

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Searching for Data in Ranges

SELECT DISTINCT fname,lname,wphone,hphone FROM

candidate c, test_taken tt WHERE c.cid=tt.cid AND integer

(score) BETWEEN 60 AND 75


candidate c, test_taken tt WHERE c.cid=tt.cid AND integer(score)

BETWEEN 60 AND 75 AND lname BETWEEN 'B' AND 'G'

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Searching for NULLs

SELECT fname,lname,wphone,hphone FROM candidate c,

test_taken tt WHERE c.cid=tt.cid AND score IS NULL

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Searching for Negative Conditions


candidate WHERE lname NOT LIKE 'S%' ORDER BY

lname,fname

SELECT fname,lname,wphone,hphoneFROM candidate c,

test_taken tt WHERE c.cid=tt.cid AND integer(score) NOT

BETWEEN 60 and 75

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Searching for Set of Values

SELECT name,phone FROM test_center tc, test_taken tt WHERE

tc.tcid=tt.tcid AND char(number) IN ('500','502')

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Subqueries

Subqueries can be used in IN clause to specify search arguments

for SQL statement.

SELECT DISTINCT name,phone FROM test_center tc, test_taken

tt WHERE tc.tcid=tt.tcid AND number IN (SELECT number

FROM test WHERE name LIKE 'DB2%')

The subquery used in this example is known as an uncorrelated

subquery.

An uncorrelated subquery is one where the values retrieved by the subquery

are not directly related to the rows processed by the outer SELECT

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A correlated subquery is a query in which subquery references

values of the outer SELECT

SELECT tc.name, count(*) FROM test_center tc,test t WHERE

tc.tcid IN (SELECT tcid FROM test_taken tt WHERE

tt.number=t.number) GROUP BY tc.name

The WHERE clause in the subquery references a table in the outer

FROM clause.

Subqueries

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Quantified Predicates

Used to compare a value or values with a collection of values.

'SOME', 'ANY', 'ALL'

SELECT c.cid, lname, fname FROM db2cert.candidate c WHERE

cid = SOME (SELECT tt.cid FROM db2cert.test_taken tt WHEREc.cid = tt.cid)

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Case Expression

SELECT fname,lname,

CASE

WHEN integer(SCORE) < 65 THEN 'Not Passed'

WHEN integer(SCORE)


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Set Operators

Union (UNION operator),

Intersection (INTERSECT operator),

Difference (EXCEPT operator).

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Union (UNION Operator)

Allows to combine results of two or more different SELECTs into

one result table.

Up to 16 different result tables can be combined using UNION

operator

Every table or SQL statement must be UNION compatible, i.e., have same

type, number, and order of columns.

UNION operator combines results of two or more separate queries

into a single result.

SELECT number,'Minimum:', MIN(integer(score))

FROM test_taken GROUP BY number

UNION

SELECT number,'Maximum:', MAX(integer(score))

FROM test_taken GROUP BY number

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Intersection (INTERSECT Operator)

To find rows that belong to two different result tables.

SELECT cid FROM candidate INTERSECT

SELECT cid FROM test_taken

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Difference (EXCEPT Operator)

Can find out which rows of one result table are not present in

another result table.

SELECT cid FROM candidate EXCEPT

SELECT cid FROM test_taken

First part of example retrieves all candidate IDs. The second

section of the query retrieves candidate IDs present in

TEST_TAKEN table. Finally, EXCEPT operator performs

difference operation that selects only those candidate IDs not

present in TEST_TAKEN table.

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Data Modifications

Inserting Rows

Updating Rows

Removing Data

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Inserting Rows

INSERT INTO test

(number,name,type,cut_score,length,totaltaken,totalpassed)

VALUES ('508','DB2 Data Propagation','P',NULL,90,0,0)

INSERT INTO test VALUES ('508','DB2 Data

Propagation','P',DEFAULT,90,79,11)

INSERT INTO test_taken

(CID,TCID,NUMBER,DATE_TAKEN,SEAT_NO) VALUES

('888','TR01','500','2000-06-04','1'),

('888','TR01','501','2000-07-11','2'),('888','TR01','502','2000-11-08','1')

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Updating Rows

UPDATE EMPLOYEE SET salary = salary + 1000 WHERE

deptid = 10 AND age > 24

UPDATE test_taken

SET (date_taken,tcid) =

(SELECT current date,tcid FROM test_center WHERE

substr(city,1,7)='Toronto' AND country='Canada')

WHERE CHAR(cid)= '888' AND number=test_id('500')

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Removing Data

DELETE FROM candidate WHERE hphone IS NULL AND

wphone IS NULL

DELETE FROM candidate WHERE cid IN (SELECT cid FROM

test_taken WHERE MONTH(date_taken)=2)

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2. Database Objects

3. Data Types


6. Indexes

7. Views

8. Identity Columns

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Index

An index is a list of locations of rows sorted by contents of one or

more specified columns.

Indexes contain a pointer, known as a record id (RID), to physical

location of rows in table.

These are two main purposes for creating indexes:

To ensure uniqueness of values

To improve query performance

There are three types of Indexes

Index

Unique Index

Clustering Index

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Unique Index

Guarantees uniqueness of data values in one or more columns.

Uniqueness is also checked during execution of CREATE INDEX

statement.

If table already contains rows with duplicate key values, index is not created.

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Referencial Integrity and Index

Primary key is maintained using an index.

Index supporting a primary key is known as primary index of

table.

Indexes supporting primary or unique key constraints cannot be

dropped explicitly.

Primary key indexes are dropped with DROP PRIMARY KEYoption.

Unique key indexes are dropped using DROP UNIQUE

(CONSTRAINT NAME) option.

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NULL Values and Indexes

Unique indexes do not enforce primary key constraint by

themselvesthey allow nulls.

Nulls, when it comes to indexing, are treated as equal to all other

nulls.

Null can not be inserted twice if the column is a key of a

unique-index because it violates uniqueness rule for index.

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Create Index Statement

CREATE UNIQUE INDEX EMP_IX ON EMPLOYEE(EMPNO)

INCLUDE(FIRSTNME,JOB)

NOTE:

Index attributes cannot be changed without recreating the index definition.

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2. Database Objects

3. Data Types


6. Index

7. Views

8. Identity Columns

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Views

Are logical tables which are derived from one or more base tables

or views.

Can be used interchangably with base tables when retrieving the

data.

Does not contain real data.

View can be ....

Updatable

Deletable

Insertable

Read-only.

NOTE: constraints defined on base table are independents of

operations that can be performed using a view.

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CREATE VIEW view1(tcid,cid,number,

date_taken,start_time,seat_no,score)AS SELECT tcid,cid,number,date_taken,start_time,seat_no,

score from test_table

WHERE tcid=center_id('TR01')

CREATE VIEW Statement

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Deletable View

A view meet all rules listed below to be considered a deletable

view...Each FROM clause of outer fullselect identifies only one base table, deletable

view , deletable nested table expression, or deletable common table expression.

The outer fullselect doesnt use VALUES clause.

The outer fullselect doesnt use GROUP BY or HAVING clauses.

The outer fullselect doesnt include column functions in its select list.The outer fullselect doesnt use set operations (UNION,EXCEPT, or

INTERSECT) with exception of UNION ALL .

The base tables in operands of a UNION ALL must not be same table, and

each operand must be deletable.

The select list of outer fullselect does not include DISTINCT .

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Updatable View

Is a special case of deletable view

A deletable view becomes a updatable view when at lease one of

its columns is updatable.

Column of a view is updatable when...

View is deletable

Column resolves to a column of a base table

All the corresponding columns of UNION ALL have exactly matching data

types (including length or precision and scale).

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Insertable Views

Allows you to insert rows using view definition.

A view is insertable when.....

All of its columns are updatable.

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Read-Only Views

Is a non-deletable view.

A view can be read-only if it does not comply with at least one of

the rules of the deletable views.

CREATE VIEW view1 (name,work_phone,home_phone) AS

SELECT DISTINCT fname,wphone,hphone FROM candidate c,

test_taken tt

WHERE c.cid = tt.cid

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Inoperative Views

Is no longer available for SQL statements.

A view becomes inoperative if...

Privilege upon which view definition is dependent, is revoked.

Object upon which view definition is dependent, is dropped

View, upon which this view definition is dependent, becomes inoperative.

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CREATE VIEW xyz(EMPNO,ENAME, DEPTNO) AS SELECT

EMPNO, ENAME, DEPTNO FROM EMPLOYEE WHEREDEPTNO = 10 WITH CHECK OPTION.

'WITH CHECK OPTION' ensures that the condition is aways

checked.

If the view is used in INSERT statement, row will be rejected if

value of DEPTNO column is not 10.

View With CHECK OPTION

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2. Database Objects

3. Data Types


6. Indexes

7. Views

8. Identity Columns

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Identity Columns

A numeric column in a table for which DB2 automatically

generates a unique numeric value for each row that is inserted intothe table

A table may have a single column that is defined with the identity

attribute

Intended to be used for generating unique primary key values

Examples: order number, employee number, stock number

Values can be generated by DB2 always or by default

Always

Values are always generated by DB2

Applications are not allowed to provide an explicit value.

By default

Values can be explicitly provided by an application or if no value is given,

then DB2 generates one

DB2 cannot guarantee uniqueness

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Creating Identity Columns

CREATE TABLE INVENTORY

(partno INTEGERGENERATED ALWAYS AS IDENTITY

(START WITH 100 INCREMENT BY 1),

description CHAR(20));

CREATE TABLE EMPLOYEES

(empno INTEGER

GENERATED BY DEFAULT AS IDENTITY

(START WITH 1000 INCREMENT BY 1 CACHE 10),

name CHAR(20));

Cache: minimum value is 2 and the maximum value is 32767

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Identity column

Must be numeric: SMALLINT, INTEGER, BIGINT, DECIMAL with precision 0Implicitly NOT NULL

Identity column does not imply a unique column. If uniqueness is required must create aunique index or primary key on the column.

START WITH n INCREMENT BY mn specifies the first value for the column, can be positive or negative, default is 1

m specifies the interval between consecutive values of the column, can be positive ornegative resulting in ascending or descending sequence

CACHE or NO CACHE

Specifies whether to keep some pre-allocated values in memory for faster access

Performance option - reduces synchronous I/O to the log when values are generated

When a database is deactivated (normally or by failure), all cached sequence values arelost

Notes:

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Inserting into Identity Columns


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CONNECT TO sample;

CREATE TABLE inventory

(partno INTEGER

GENERATED ALWAYS AS IDENTITY (START WITH 100 INCREMENT BY 1),

description CHAR(20) );

COMMIT;

INSERT INTO inventory VALUES (DEFAULT,'door'); --->inserts 100,door

INSERT INTO inventory (description) VALUES ('hinge'); --->inserts 101,hinge

INSERT INTO inventory VALUES (200,'windor'); --->error

COMMIT;

INSERT INTO inventory (description) VALUES ('lock'); --->inserts 102,lock

ROLLBACK;

INSERT INTO inventory (description) VALUES ('frame'); --->inserts 103,frame

COMMIT;

SELECT * FROM inventory;

100 door

101 hinge

103 frame

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Inserting into Identity ColumnsCONNECT TO sample;

CREATE TABLE inventory

(partno INTEGER PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY (START WITH 100 INCREMENT BY 1),

description CHAR(20) );

COMMIT;

INSERT INTO inventory VALUES (DEFAULT,'door'); --->inserts 100,door

INSERT INTO inventory (description) VALUES ('hinge'); --->inserts 101,hinge

INSERT INTO inventory VALUES (200,'window'); --->inserts 200,window

INSERT INTO inventory VALUES (102,'handle'); --->inserts 102,handleINSERT INTO inventory VALUES (101,'bolt'); --->error, duplicate

COMMIT;

INSERT INTO inventory (description) VALUES ('lock'); --->error, duplicate

INSERT INTO inventory (description) VALUES ('lock'); --->inserts 103,lock

ROLLBACK;

INSERT INTO inventory (description) VALUES ('frame'); --->inserts 104,frameCOMMIT;

SELECT * FROM inventory order by partno;

100 door

101 hinge

102 handle

104 frame

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Retrieving Generated Value

Function available to retrieve the last value generated:

identity_val_local()Must be used with a VALUES clause

Function has no input parameter

Result returned is a DECIMAL(31,0) data type, regardless of the actual

data type of the identity column

Function returns the most recently assigned value for an identity column,where the assignment occurred as a result of a single row INSERT

statement

Value can only be retrieved within the same unit of work as the INSERT

statement

The assigned value could be values supplied by the user or by DB2

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IDENTITY VAL LOCAL()


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IDENTITY_VAL_LOCAL()

(SET AUTOCOMMIT OFF)

CONNECT TO sample;

CREATE TABLE T1

( C1 INTEGER GENERATED ALWAYS AS IDENTITY,

C2 INTEGER ) ;

INSERT INTO T1 (C2) VALUES (5);

INSERT INTO T1 (C2) VALUES (6);SELECT * FROM T1;

C1 C2

----- -----

1 5

2 6

VALUES IDENTITY_VAL_LOCAL( );

IDENTITY_VAL_LOCAL( )

--------------------

2

COMMIT;

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Notes:


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Identitymissing: when input data file does not contain any values for the identitycolumn. Example: a table tab1 has C1 identity, C2, C3, C4 columns. Input filecontains data for columns C2, C3 and C4 only. To invoke load:

load from data.del of del replace into tab1 (C2,C3,C4) ....is equivalent to...

load from data.del of del modified by identitymissing replace into table1

Identityignore: even though the input data file contains data for the identity column,

the data should be ignored and identity values should be generated for each row.

Identityoverride: used for loading user-supplied values into a table having aGENERATED ALWAYS identity column. Useful when migrating data from anotherdatabase.

Notes:

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Advanced SQL1. User Defined Data Types

2. Sequences


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User Defined Types


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User Defined Types

User defined distinct types

User defined structured types

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User Defined Types


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User-defined distinct type :

Can be created on an existing data type.

Strong typing:

If columns are defined using different UDTs based on the same

base data type, these UDTs cannot be directly compared.

Only functions/operators defined on distinct type can be applied

to its instances.

Hence DB2 does not allow direct comparison between 'distinct'

type and 'source' type (ie. US_DOLLAR and DECIMAL)

Casting functions:

When UDTs are defined, system-generated SQL functions are

created.

Casting functions allow comparison between the UDT and its

base type.

User Defined Types

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CREATE DISTINCT TYPE pound AS INTEGER WITH COMPARISONS

CREATE DISTINCT TYPE kilogram AS INTEGER WITH

COMPARISONS

CREATE TABLE health (f_name VARCHAR(30), weight_p POUND,

weight_k KILOGRAM)

SELECT f_name, weight_p FROM health WHERE weight_p > POUND(30)

User Defined Types

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CREATE DISTINCT TYPE PHONENO AS CHAR(10)

WITH COMPARISONS

Creation of this user-defined data type will result in

creation of following casting functions:

CHAR(PHONENO): translates data values from the

PHONENO data type to base data type CHAR

PHONENO(CHAR): translates data values from base

data type CHAR to PHONENO data type

User Defined Types

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CREATE DISTINCT TYPE US_DOLLAR AS DECIMAL(9,2)

WITH COMPARISONS

CREATE TABLE US_SALES (

PRODUCT_ITEM INTEGER,

YEAR INTEGER CHECK(YEAR>1985),

TOTAL US_DOLLAR)

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As a part of distinct type generation, DB2 generates 'cast' function.

E.g.

SELECT PRODUCT_ITEM FROM US_SALES WHERE TOTAL >

US_DOLLAR(100000)

OR

SELECT PRODUCT_ITEM FROM US_SALES WHERE TOTAL > CAST(100000 AS US_DOLLAR)

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Important Functions...


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CREATE FUNCTION SUMDOLLAR(US_DOLLAR) RETURNS

US_DOLLAR SOURCE SYSIBM.SUM(DECIMAL())

SELECT SUMDOLLAR(TOTAL) FROM US_SALES

CREATE FUNCTION DOLLAR_AVG(US_DOLLAR)

RETURNS DECIMAL SOURCE SYSIBM.AVG(DECIMAL())

SELECT DOLLAR_AVG(TOTAL) FROM US_SALES

Important Functions...

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Important Functions

SELECT DOLLAR_AVG(TOTAL) - 10 FROM US_SALES

SELECT ((SELECT DOLLAR_AVG(TOTAL) FROM

US_SALES WHERE YEAR = 1987)- (SELECT

DOLLAR_AVG(TOTAL) FROM US_SALES WHERE

YEAR=1986)) FROM US_SALES

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'Structured types' are useful for modelling objects that have a well

defined structure consisting of 'attributes'.

CREATE TYPE ADDRESS_T AS (

HOUSE CHAR(15),

STREET1 CHAR(15),

STREET2 CHAR(15),

CITY CHAR(15),

PIN CHAR(6)) MODE DB2SQL


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Inheritance:

CREATE TYPE PERSON_T AS(NAME CHAR(15),

AGE INT, ADDRESS ADDRESS_T) MODE DB2SQL

CREATE TYPE EMP_T

UNDER PERSON_TAS (EMPCODE INT, SALARY DECIMAL(9,2))

MODE DB2SQL

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g yp

CREATE TABLE PERSON OF PERSON_T (REF IS OID USER

GENERATED)

CREATE TABLE EMP OF EMP_T UNDER PERSON INHERIT

SELECT PRIVILEGES

INSERT INTO PERSON(OID,NAME,AGE,ADDRESS)

VALUES(PERSON_T('a'),'Gopal',28,

ADDRESS_T()..HOUSE('house1')..STREET1('MG Road')

..STREET2('Off High Way')..CITY('Mumbai')..PIN('400063'))

INSERT INTO PERSON (OID,NAME,AGE,ADDRESS)

VALUES (PERSON_T(GENERATE_UNIQUE()),

'Prakash',28,ADDRESS_T()..HOUSE('house2')..STREET1('L T

Road')..STREET2('Off high Way')..PIN('400063'))

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In typed table definition, columns can be defined as reference

columns to another typed table.Referenced typed table is called a target table.

A reference column holds values that correspond to OID values of

target table and clearly identify rows in target tables.

Data type of a reference column is REFERENCE , the same type

as OID in target table.

Reference column is similar to foreign key; however, evaluation,like a foreign key, is not performed for operations such as insert,

update, or delete.

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CREATE TYPE DEPT_T AS (NAME CHAR(40), LOCATION CHAR(20))

REF USING INTEGER MODE DB2SQL

CREATE TYPE EMP_T UNDER PERSON_T AS (SALARY INTEGER,

DEPTREF REF(DEPT_T)) MODE DB2SQL

Deptref REF(Dept_t) means that this attribute DEPTREF of EMP_T type is

reference type and target of reference is a row of table whose row type is

DEPT_T or its sub-type.

CREATE TABLE DEPT OF DEPT_T (REF IS Oid USER GENERATED)

CREATE TABLE EMP OF EMP_T UNDER PERSON INHERIT SELECT

PRIVILEGES (DEPTREF WITH OPTIONS SCOPE Dept)

DEPTREF WITH OPTIONS SCOPE DEPT means that values in column

DEPTREF are pointing to rows in table DEPT or values in any sub-tables of

DEPT table.

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Selecting Rows From Typed Table


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g yp

When a select statement is issued for a typed table, rows are

returned from target table and all of its sub-tables in tablehierarchy.

For retrieving rows of only PERSON table...

SELECT * FROM ONLY(Person)

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SELECT NAME,AGE,

ADDRESS..HOUSE,

ADDRESS..STREET1,

ADDRESS..STREET2,

ADDRESS..CITY,

ADDRESS..PIN FROM PERSON

g yp

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Updating And Deleting Rows From Typed Tables


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UPDATE Person SET birthyear=1969 WHERE oid=Emp_t(10)

DELETE FROM Person

Deletes all rows from PERSON table and its sub-tables.

DELETE FROM ONLY(Person)

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2. Sequences


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Sequences


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q

SEQUENCE object lets DBA or developer create a value that gets

incremented under programmer control and can be used acrossmany different tables.

CREATE SEQUENCE CUSTOMER_NO AS INTEGER

By default this sequence number starts at one and increments by one at a time

and is of an INTEGER datatype.

NEXTVAL :

Function generates next value for sequence which can then be used for

subsequent SQL statements

INSERT INTO CUSTOMERS VALUE (NEXTVAL FORCUSTOMER_NO, 'Prakash', ...)

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Sequences


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PREVVAL:

Will only return last value generated by that application.Function can be used multiple times within application.

INSERT INTO INVOICES (34,PREVVAL FOR

CUSTOMER_NO, 234.44, ...)

If customer number generated, needs to be used for a subsequent invoicerecord.

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2. Sequences


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Advance Functions


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Trigonometric Functions

COS , SIN , TAN , COT , TANH , COSH , SINH , ATAH , ATAN2

Math Functions

INTEGER , FLOOR , CEILING , TRUNC , SQRT , LN , EXP

String Functions

RTRIM,LTRIM,INSTR,TRANSLATE,REPEAT,REPLACE,CONCAT,

SUBSTR, LENGTH , LOWER/LCASE , UPPER/UCASE

Statistical Functions

CORRELATION , STDDEV , VARIANCE

Date Functions

DATE , TIME , TO_CHAR , TO_DATE , DAYNAME , DAYOFWEEK

Logic FunctionsCOALESCE , NULLIF

Speciality Functions

MQPUBLISH , MQREAD , ENCRYPT , REC2XML

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Summary


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SQL

SQL Getting StartedDatabase Objects

Data Types, Constraints, Rules

Data Definition Language

Data Manipulation Language

Indexes

ViewsIdentity Columns

Advanced SQLUser Defined Data Types

Sequences

Advanced Functions

04sql and advanced sql

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