SQL Components DML DDL DAL

Overview u Getting the records onto the disk - mapping u Managing disk space u SQL Modes u Ceating database

Differing Vantages UserDeveloper Administrator Access Inquiry Entry Definition Relation Organization Validation Recovery Protection Storage D B M S

DB Language Modes DML - Data Manipulation Language - enter, inquire, update, delete data from end user or programming language DDL - Data Definition Language - define database objects, attributes and characteristics at conceptual and physical layers DAL - Data Administration Language - grant and revoke data access privileges, manage physical data configuration, perform backup and recovery functions

Tables Basic storage structure Base tables –stored on the disk –constraints always upheld Virtual tables –not stored, transient –join tables Views

Primary Keys u Uniquely identifies tuple u All base tables must have primary key u Role of PK –prevent duplicate rows –assure existence of data u Information should not be encoded into primary keys

Composite Primary Key u Primary key may be composed of more than one attribute u Composite primary key should be minimal subset u Unique identifier simplifies lengthy compound primary key

Foreign Key u An attribute in one table refers to a primary key in another table u Relationships formed through foreign keys but not exclusively

SQL DDL CREATE TABLESPACE –allocates default space for table creation CREATE TABLE –makes base tables »define field size »determine field data types »name primary key »define foreign keys »include all constraints

Table creation CREATE TABLE SALESPERSON (SNUMBER VARCHAR2(2)PRIMARY KEY, LAST VARCHAR2(10), FIRST VARCHAR2(8), STREET VARCHAR2(15), CITY VARCHAR2(15), STATE VARCHAR2(2), ZIP_CODE VARCHAR2(9), COMMISSION NUMBER(8,2), COMMISSION_RATE NUMBER(4,2) ); DROP TABLE SALESPERSON;

DATA TYPES l NUMBER t NUMBER(9) t number(8,2) t NUMBER(8,1) t NUMBER(5)exceeds precision l VARCHAR2(size) t Variable length character string l DATEDD-MMM-YY t date arithmetic t sysdate

SQL DML SELECT –returns table containing all records meeting criteria UPDATE –makes changes to column contents based on provided specifications INSERT –adds rows, placing data in some or all of the columns DELETE

INSERTS Insert into emp values (4243, 'OTTER', 'ENGINEER', 4234, '20-JUN-95', 2900, NULL, 40); Insert into emp (empno, ename, hiredate) values(1235, 'KINNEY', 22-JUN-95'); Insert into emp (job, mgr,sal, deptno) select job, mgr, 2500, deptno from emp where ename = 'AUGUST';

Update Rows u UPDATE SALESPERSON SET COMMISSION_RATE = COMMISSION_RATE+.05 WHERE COMMISSION_RATE <.15;

Delete u DELETE FROM SALESPERSON; u DELETE FROM SALESPERSON WHERE STATE = ‘MA’; u DELETE FROM SALESPERSON WHERE ZIP_CODE IN (SELECT ZIP FROM ANOTHER WHERE CITY = ‘BOSTON’;

SQL DAL GRANT –Grant access to other users BACKUP AUDIT SYSTEM TABLES