4) working with db2 data using sql and xquery ppt

8/9/2019 4) Working With DB2 Data Using SQL and XQuery PPT

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IBM DB2 9

Section -4) Working with DB2 DataWorking with DB2 Datausing SQL and XQueryusing SQL and XQuery

2008 IBM Corporation

Amit DaharwalIT Specialist IBM Academic Initiative


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Section 4Section 4 -- Working with DB2 Data usingWorking with DB2 Data usingSQL and XQuery (23.5%)SQL and XQuery (23.5%)

Given a DML SQL statement, ability to identify resultsGiven a DML SQL statement, ability to identify results

Ability to use SQL to SELECT data from tablesAbility to use SQL to SELECT data from tables

Ability to use SQL to SORT or GROUP dataAbility to use SQL to SORT or GROUP data

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, ,, , Knowledge of transactions (i.e., COMMIT, ROLLBACK,Knowledge of transactions (i.e., COMMIT, ROLLBACK,

and transaction boundaries)and transaction boundaries)

Ability to call a procedure or invoke a user definedAbility to call a procedure or invoke a user definedfunctionfunction

Given an XQuery statement, knowledge to identify resultsGiven an XQuery statement, knowledge to identify results


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

Designed to access tabular data.

Invented by IBM in the 1970s, the SQL language continues toevolve and is the only way to access relational database data.

Three major categories.

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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 objectaccess control


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Managing Database Objects - DDLTo create, modify, delete objects in a database, SQL Data

Definition Language (DDL) is used.

DDL has four basic SQL statements:

CREATE

To create objects in a database.

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DECLARETo create Temporary Tables in a database.

ALTER

To make permitted alteration in structure of an object.DROP

To remove any object created with CREATE/ DECLAREstatements from database.


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Manipulate Data - DMLTo retrieve, insert, update or delete from tables and/or views,

SQL Data Manipulation Language (DML) is used.

DML also has four basic SQL statements:

SELECT

To retrieve data from table or view.

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INSERTTo add records in tables.

UPDATE

To change data.

DELETE

To delete records from tables.


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Using SELECT to Retrieve DataThe SELECT statement is used to retrieve table or

view data.

Syntax -

SELECT [DISTINCT] columns

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WHERE condition

GROUP BY column

HAVING conditionORDER BY column


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Examples -SELECT * FROM staff;

SELECT * FROM staffFETCH FIRST 10 ROWS ONLY;

SELECT name, salar

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FROM staff;

SELECT DISTINCT dept, job

FROM staff;SELECT name, salary + comm AS pay

FROM staff;


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CASE Expressions In SELECTSELECT empno, lastname, job, salary,

CASE WHEN job IN ('MANAGER, ADMIN)

THEN salary * 1.10

WHEN job IN ('DBA, ARCHITECT)

*

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.

WHEN job = 'PROGRAMMER'

THEN salary * 1.05

ELSE salary * 1.035END as new_salary

FROM employee


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With WHERE clauseUse the WHERE clause to select specific rows from a table or

view.

Relational operators including:

=, >, =,


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Using Functions to Transform DataScalar functions

Also known as row functions

Operate on a single value to return another single

value.

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, , , , ,

DAY(), LCASE(), LOWER(), UCASE() or UPPER()

Column functions

Also known as vector functions.Work on a group of rows to provide a result.

SUM(), AVG(), MIN(), MAX(), COUNT()


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Using Set Operators to Combine Multiple QueriesWith DB2, it is possible to combine two or more queries into a

single query by using a special operator known as a set

operator. When a set operator is used, the results of eachquery executed are combined in a specific manner to produce

a single result data set

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are combined and all duplicate rows are eliminated

INTERSECT - common records that are found in both the result

data sets will be shown as final result set.

EXCEPT - all records found in the first result data set that donot have a corresponding record in the second result data set

will be shown as final result set.


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SELECT lastname, hiredate FROM employee

WHEREMONTHNAME(hiredate) = 'December' AND

salaryNOT BETWEEN 20000.00 AND 90000.00

SELECT * FROM emp_exp_02 UNIONSELECT * FROM emp_exp_01

SELECT empno, lastname FROM employee

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as name empnoSELECT COUNT(*) FROM employee WHERE

workdept IN (SELECT deptno FROM department

WHERE admrdept = 'A00')

SELECT workdept, DECIMAL(AVG(salary), 9, 2)

AS avg_salary FROM employee GROUP BY work

dept HAVINGAVG(salary) > 60000


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Using Joins - Concepts Ajoin combines data from two or more tables. A join

condition is required to refine the result set (eliminates acartesian product). Joining can be INNER or OUTER.

INNER JOIN - Keeps only the rows from the cross productthat meet the join condition. Result set of inner join consistonl those match rows that are resent in both oin table.

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OUTER JOIN is a concatenation of the inner join and rowsfrom the left table, right table, or both tables that are missing

from the inner join. There are 3 types of Outer Join.

1. Left outer join = inner join + rows from the left table2. Right outer join = inner join + rows from the right table

3. Full outer join = inner join + the rows from both the tables


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Using Joins ExamplesSELECT lastname, deptname FROM employee e,

department d WHERE e.workdept = d.deptno

ORSELECT lastname, deptname FROM employee e INNER

JOIN department d ON e.workdept = d.deptno

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SELECT lastname, deptname FROM employee e LEFTOUTER JOIN department d ON e.workdept = d.deptno

SELECT lastname, deptname FROM employee e RIGHT

OUTER JOIN department d ON e.workdept = d.deptnoSELECT lastname, deptname FROM employee e FULL

OUTER JOIN department d ON e.workdept = d.deptno


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INSERT StatementThe INSERT statement is used to add new rows to a

table or a view.

Examples:INSERT INTO staff VALUES

(1212,'Cerny',NULL,'Sales',3)

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INSERT INTO staff (id, name, dept, job, years)

VALUES (1212,'Cerny',20,'Sales',3),

(1213,'Wolfrum',20,NULL,2)

INSERT INTO department (deptno, deptname)

SELECT deptno, deptname FROM sales_depts


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IBM DB2 9

UPDATE StatementThe UPDATE statement is used to change the data in

a table or a view.

For example:

UPDATE staff SET dept = NULL

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ename

UPDATE staff SET (dept, sal)=(51, 7000)

WHERE id = 750

UPDATE employees SET (dept) =(SELECT deptname FROM department

WHERE deptno = 1)


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IBM DB2 9

DELETE StatementThe DELETE statement is used to delete entire rows

of data from a table.

For example:

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DELETE FROM staff WHERE id IN (1212, 1213)

DELETE FROM sales WHERE salesperson IS NULL


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The COMMIT and ROLLBACK statementsA unit of work (UOW), also known as a transaction, is a

recoverable sequence of operations within an application

process. Ex. transfer funds transaction.

The application ends the UOW by issuing either a COMMIT or

a ROLLBACK statement, whichever is appropriate.

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e s a emen ma es a c anges ma e w n e

UOW permanent, whereas the ROLLBACK statement reverses

those changes.

If the application ends normally without an explicit COMMIT or

ROLLBACK statement, the UOW is automatically committed. If the application ends abnormally before the end of a UOW,

that unit of work is automatically rolled back.


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IBM DB2 9

SavepointsA savepoint lets you selectively roll back a subset of actions

that make up a UOW without losing the entire transaction.

do some work;savepoint s1 on rollback retain cursors

do some more work

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savepoint s2 on rollback retain cursorsdo even more work;

savepoint s3 on rollback retain cursors

wrap it up;roll back to savepoint s1;


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What is XML? XML was designed to structure, store and to send

data/information.

At its core XML is text formatted in the form of tags and textthat follow a well-defined set of rules.

This text may be stored/represented in:

John Smith Co

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A normal file stored on diskA message being sent over HTTP

A character string in a programming language

A CLOB (character large object) in a database

Any other way textual data can be used

1234 W. Main St

ToledoOH95141

A5412

985

1


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XML specifications

XMLdocument

s

DTDdescribes

supersedes

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XSD

XQuery XPath

XSLT

searches searches transforms

uses

uses

uses

uses


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XPath Expressions

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XML Facilities XML data type for columns

create table s1.t1 (c1 int, c2 xml)

Language bindings for XML type in programming languages

cobol, c, java, etc..

XML indexes

create ix1 on s1.t1(c2) generate keys using pattern /dept/emp/@empno

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An XML schema/DTD repository

Support forXQuery as a primary language as well as:

Support forSQL within XQuery

Support forXQuery with SQL

Support for new SQL/XML functions

Performance, scale, and everything else they expect from a

DBMS


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IBM DB2 9

Two ways to query XML data in DB2

Using XQuery as the primary language

All queries begin with XQuery.

Tells the DB2 parser what to expect

Can execute SQL within a query beginning with XQUERY

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Using SQL as the primary language

Part 2


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XQuery: The FLWOR Expression

FOR: iterates through a sequence, bind variable to items LET: binds a variable to a sequence WHERE: eliminates items of the iteration

ORDER: reorders items of the iteration RETURN: constructs query results

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,

xqueryfor $d in db2-fn:xmlcolumn(dept.deptdoc)/dept

let $emp := $d//employee/name

where $d/@bldg > 95

order by $d/@bldgreturn

{$d/@bldg, $emp}

John Doe

408 555 1212

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Peter Pan

408 555 9918

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Input:


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FLWOR Expression

xquery

for $d in xmlcolumn(deptdoc)/dept

where $d/@bldg = 101return

{$d/employee/name}

xquery

for d in xmlcolumn de tdoc /de t

John Doe

408 555 1212344

Peter Pan

408 555 9918

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create table dept (deptID char(8), deptdoc xml);

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John DoePeter Pan

John Doe

Peter Pan

John DoePeter Pan

This result is not an XML document!

xquery

for $d in xmlcolumn(deptdoc)/dept

where $d/@bldg = 101

return $d/employee/name/text()

where $d/@bldg = 101

return $d/employee/name


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Two ways to query XML data in DB2

Using XQuery as the primary language

Done

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Looking at query onlyAll queries begin with Select

XML Retrieval done with XMLQUERY (flags db2 parser to

switch to XML Processing)

IBM DB2 9


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XML Functions

XMLQUERY(). function that enables you to execute an XQueryexpression from within an SQL context. It returns an XMLvalue, which is an XML sequence. This sequence can be

empty or it can contain one or more items.

XMLTABLE(). returns a table from the evaluation of XQuery

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sequence, however, XMLTABLE() allows you to execute anXQuery expression and return values as a table instead.

XMLEXISTS(). If it returns an empty sequence, XMLEXISTS

returns FALSE; otherwise, TRUE is returned. The XMLEXISTSpredicate can be used in the WHERE clauses of UPDATE,DELETE, and SELECT statements.

IBM DB2 9


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DML statements for XML Data

INSERT INTO customers (custinfo) VALUES (

XMLPARSE(DOCUMENT 'John Doe'

PRESERVE WHITESPACE))

DELETE FROM customer WHERE XMLEXISTS ('declare

default element namespace "http://custrecord.dat";

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$info/customerinfo[name/text()=" John Doe"]'

PASSING custinfo AS "info")

UPDATE customer

SET custinfo = XMLPARSE (DOCUMENT JaneDoe PRESERVE WHITESPACE)

WHERE empno = 11;

IBM DB2 9


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XMLTABLE - XML to relationalSELECT X.* fromXMLTABLE (db2-fn:xmlcolumn(PORDERS.PO)//customer

COLUMNS

CID INTEGER PATH @id,Name VARCHAR(30) PATH name,ZipType CHAR(2) PATH zip/@type,Zip XML PATH zip

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95023USnull4711

33129USBobby1325

ZipZipTypeNameCID

IBM DB2 9


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Given the following queries:

SELECT c1 FROM tab1; SELECT c1 FROM tab2;

Which of the following set operators can be used to

produce a result data set that contains only recordsthat are not found in the result data set produced by

each query after duplicate rows have been

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eliminated?A. UNION

B. INTERSECT

C. EXCEPT

D. MERGE

IBM DB2 9


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Given the following UPDATE statement:

UPDATE employees SET workdept = (SELECT deptno FROM

department WHERE deptno = 'A01') WHERE workdept IS NULL

Which of the following describes the result if this statement is

executed?

A. The statement will fail because an UPDATE statement cannot

contain a subquery.

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B. The statement will only succeed if the data retrieved by thesubquery does not contain multiple records.

C. The statement will succeed; if the data retrieved by the subquery

contains multiple records, only the first record will be used to perform

the update. D. The statement will only succeed if every record in the

EMPLOYEES table has a null value in the WORKDEPT column.

IBM DB2 9


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Given the following SALES table definition:

SALES_DATE DATE

SALES_PERSON CHAR(20)

REGION CHAR(20)

SALES INTEGERWhich of the following SQL statements will remove all rows that

had a SALES_DATE in the year 1995?

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A. DELETE * FROM sales WHERE YEAR(sales_date) = 1995

B. DELETE FROM sales WHERE YEAR(sales_date) = 1995

C. DROP * FROM sales WHERE YEAR(sales_date) = 1995D. DROP FROM sales WHERE YEAR(sales_date) = 1995

IBM DB2 9


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Given the following EMPLOYEEStable definition:

EMP ID INTEGERNAME CHAR(20)

DEPT CHAR(10)

SALARY DECIMAL (10, 2)

COMMISSION DECIMAL (8, 2)Assuming the DEPT column contains the values 'ADMIN', 'PRODUCTION',

and 'SALES', which of the following statements will produce a result data set

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,

PRODUCTION department employees are grouped together, and all SALESdepartment employees are grouped together?

A. SELECT name, dept FROM employees ORDER BY dept

B. SELECT name, dept FROM employees GROUP BY dept

C. SELECT name, dept FROM employees GROUP BY ROLLUP (dept)

D. SELECT name, dept FROM employees GROUP BY CUBE (dept)

IBM DB2 9


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Given the following EMPLOYEEStable definition:

EMP ID INTEGERNAME CHAR(20)

DEPT CHAR(10)

SALARY DECIMAL (10, 2)

COMMISSION DECIMAL (8, 2)Assuming the DEPT column contains the values 'ADMIN', 'PRODUCTION',

and 'SALES', which of the following statements will produce a result data set

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,

PRODUCTION department employees are grouped together, and all SALESdepartment employees are grouped together?

A. SELECT name, dept FROM employees ORDER BY dept

B. SELECT name, dept FROM employees GROUP BY dept

C. SELECT name, dept FROM employees GROUP BY ROLLUP (dept)

D. SELECT name, dept FROM employees GROUP BY CUBE (dept)

IBM DB2 9


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Which of the following best describes a unit of work?

A. It is a recoverable sequence of operations whose point ofconsistency is established when a connection to a databasehas been established or when a mechanism known as asavepoint is created.

B. It is a recoverable sequence of operations whose currentpoint of consistency can be determined by querying the system

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.

C. It is a recoverable sequence of operations whose point ofconsistency is established when an executable SQL statementis processed after a connection to a database has beenestablished or a previous transaction has been terminated.

D. It is a recoverable sequence of operations whose point ofconsistency is only established if a mechanism known as asavepoint is created.

IBM DB2 9


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A stored procedure has been created with thefollowing statement:CREATE PROCEDURE proc1 (IN

var1 VARCHAR(10), OUT rc INTEGER) SPECIFIC

myproc LANGUAGE SQL What is the correct way

to invoke this procedure from the command line

processor (CLP)?

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A. CALL proc1 ('SALES', ?)B. CALL myproc ('SALES', ?)

C. CALL proc1 (SALES, ?)

D. RUN proc1 (SALES, ?)

IBM DB2 9


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4) working with db2 data using sql and xquery ppt

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