Structured Query Language

Brief History• Developed in early 1970 for relational data

model:– Structured English Query Language (SEQUEL)– Implemented with IBM System R

• 1987 first ISO standard version• 1992 SQL 2• 1999 SQL 3

– Object-relational model

• 2003:SQL 2003– SQL/XML

• Products: DB2, Oracle, MS SQL, MySQL

Oracle Account

• Server: libra.sfsu.edu • Telnet: libra.sfsu.edu

• How to use Oracle:– http://www.sfsu.edu/~helpdesk/docs/using/usingoracle.htm

• Basic Unix commands:– http://www.sfsu.edu/~helpdesk/docs/using/unixcmd.htm

• You may also use MySQL for assignments and project.

Other DBMS

• MySQL 5.0:– http://dev.mysql.com/downloads/

• MS SQL Server 2005 Express:– http://msdn.microsoft.com/vstudio/express/sql/

download/

Language Overview

• Three major components:– Data definition language

• Create Table– Data manipulation language

• Updating database:– Insert, Delete, Update

• Query database:– Select

– Data control language (DCL)• Help DBA control the database:

– Grant/revoke privileges to access the database, creating procedures, etc.

• Interface with database:– Entering command interactively at the DBMS command prompt.– Embedded in a procedural language

Data Definition Language

• SQL Identifiers– Character set: A-Z, a-z, 0-9, _– <= 128 characters– Start with a letter– Cannot contain spaces

SQL Data Types• Boolean

– True, False, Unknown (for Null)• Character

– Fixed length: CHARACTER(n), CHAR(n), CHAR – default to 1 character– Varying length:

• CHARACTER VARYING(n): Maximum length is n• VARCHAR(n)

• Numeric– NUMERIC(i,j), DECIMAL(i,j), DEC(i,j)– INTEGER, INT, SMALLINT – up to 32767– FLOAT, REAL, DOUBLE PRECISION

• Date:– DATE– TIME– TIMESTAMP

• Large objects:– CHARACTER LARGE OBJECT– BINARY LARGE OBJECT

CREATE TABLE

• CREATE TABLE tableName(fields and data type separated by commas);

• Ex.– CREATE TABLE employee(

eid CHAR(5),

ename VARCHAR(40),

sex CHAR,

salary NUMERIC(9,2),

hire_Date DATE);

Integrity Enhancement Feature• Required data: NOT NULL

– eid CHAR(5) NOT NULL,• Default value:DEFAULT

sex CHAR DEFAULT ‘M’,

• Field domain: CHECK(condition)– salary NUMERIC(9,2) CHECK (salary >= 100 AND salary

<=10000),– sex CHAR DEFAULT ‘M’ CHECK (sex in (‘M’,’F”)),

• PRIMARY KEY– PRIMARY KEY(sid)– PRIMARY KEY(sid, cid)

• Unique – allow null value, the PRIMARY KEY constraint does not allow null.– ESSN CHAR(9) UNIQUE

– CREATE TABLE employee(eid CHAR(5) PRMARY KEY,

ename VARCHAR(40),

sex CHAR DEFAULT ‘M’ CHECK (sex in (‘M’,’F”)),

salary NUMERIC(9,2),

hire_Date DATE);

• create table orderdetail

• (oid char(3), cid char(5), qty numeric(5,2),

• primary key (oid,cid));

ALTER TABLE

• ADD/Modify/DROP COLUMN a new field from a table.

• Ex.ALTER TABLE employee

ADD phone CHAR(8);ALTER TABLE employee

Modify phone CHAR(9);ALTER TABLE employee

DROP COLUMN Phone;

Adding Constraints with the ALTER TABLE command

• Constraints:– PRIMARY KEY, CHECK, UNIQUE

• PRIMARY KEY:– ALTER TABLE tablename– ADD CONSTRAINT constraintname– PRIMARY KEY (columnname);

• CHECK– ALTER TABLE tablename– ADD CONSTRAINT constraintname– CHECK (criteria);

Examples

ALTER TABLE emp

ADD CONSTRAINT empkey PRIMARY KEY (empid);

ALTER TABLE empADD CONSTRAINT validSalary CHECK (salary between 100 AND 20000);

Note: Constraints information are stored in table: USER_CONSTRAINTS. You can use the DESCRIBE command to show fields in this table.

Dropping Constraints

ALTER TABLE tablename

DROP CONSTRAINT constraintname;

Disable/Enable Constraints

• ALTER TABLE tablename

• DISABLE CONSTRAINT constraintname;

• ALTER TABLE tablename

• ENABLE CONSTRAINT constraintname;

Creating Table Through SubQuery

• CREATE TABLE tableName

• AS (Select query)

• Ex.– CREATE TABLE newEmp– AS (SELECT empid, ename,salary FROM

emp);

Renaming a Table

• Rename oldName to newName

Removing a Table

• DROP TABLE tableName

SQL Insert CommandINSERT INTO tableName VALUES (field values separated by commas);

INSERT INTO tableName (Column names separated by commas)VALUES (field values separated by commas);

Ex 1. Customer table with CID, CNAME, CITY, RATING.

a. INSERT INTO CUSTOMER VALUES (‘C1’, ‘SMITH’, ‘SF’, ‘A’);

b. INSERT INTO CUSTOMER (CID, CNAME,RATING) VALUES (‘C1’, ‘SMITH’, ‘A’);

Record with Date Field

• Oracle date format: – ‘dd-mmm-yyyy’

• Example:• insert into orders values('O7','c2','s1','10-oct-2007');

Inserting records from an existing table

• INSERT INTO stu2

• (select * from student);

SQL Delete Command

DELETE FROM tableName [WHERE criteria];

Ex 1. Delete a record from the Customer table.

DELETE FROM CUSTOMER WHERE CID = ‘C1’;

SQL Update Command

UPDATE tableName SET field = new value [WHERE criteria];

Ex 1.

UPDATE CUSTOMER SET RATING = ‘A’ WHERE CID=‘C1’;

Ex 2.

UPDATE CUSTOMER SET CITY = ‘SF’, RATING = ‘A’ WHERE CID=‘C1’;

Dealing with Null

• Null is a key word. We can use Null in the INSERT, UPDATE, and DELETE command.

• Use IS NULL (or IS NOT NULL) in a criteria.• Examples:

– INSERT INTO emp VALUES (‘e95’,’June’,’f’,NULL,5000);

– UPDATE emp SET salary=null where empid=‘e99’;– SELECT * FROM emp WHERE salary IS NULL;– SELECT * FROM emp WHERE salary= NULL (not

working);