1. © 2007 by Prentice Hall (Hoffer, Prescott & McFadden) 1 Introduction to SQL

2. Chapter 7 © 2007 by Prentice Hall 2 SQL Overview Structured Query Language Structured Query Language The standard for relational database management systems (RDBMS) The standard for relational database management systems (RDBMS) RDBMS: A database management system that manages data as a collection of tables in which all relationships are represented by common values in related tables RDBMS: A database management system that manages data as a collection of tables in which all relationships are represented by common values in related tables

3. Chapter 7 © 2007 by Prentice Hall 3 History of SQL 1970–E. Codd develops relational database concept 1970–E. Codd develops relational database concept 1974-1979–System R with Sequel (later SQL) created at IBM Research Lab 1974-1979–System R with Sequel (later SQL) created at IBM Research Lab 1979–Oracle markets first relational DB with SQL 1979–Oracle markets first relational DB with SQL 1986–ANSI SQL standard released 1986–ANSI SQL standard released 1989, 1992, 1999, 2003–Major ANSI standard updates 1989, 1992, 1999, 2003–Major ANSI standard updates Current–SQL is supported by most major database vendors Current–SQL is supported by most major database vendors

4. Chapter 7 © 2007 by Prentice Hall 4 Purpose of SQL Standard Specify syntax/semantics for data definition and manipulation Specify syntax/semantics for data definition and manipulation Define data structures Define data structures Enable portability Enable portability Specify minimal (level 1) and complete (level 2) standards Specify minimal (level 1) and complete (level 2) standards Allow for later growth/enhancement to standard Allow for later growth/enhancement to standard

5. Chapter 7 © 2007 by Prentice Hall 5 Benefits of a Standardized Relational Language Reduced training costs Reduced training costs Productivity Productivity Application portability Application portability Application longevity Application longevity Reduced dependence on a single vendor Reduced dependence on a single vendor Cross-system communication Cross-system communication

6. Chapter 7 © 2007 by Prentice Hall 6 SQL Environment Catalog Catalog A set of schemas that constitute the description of a database A set of schemas that constitute the description of a database Schema Schema The structure that contains descriptions of objects created by a user (base tables, views, constraints) The structure that contains descriptions of objects created by a user (base tables, views, constraints) Data Definition Language (DDL) Data Definition Language (DDL) Commands that define a database, including creating, altering, and dropping tables and establishing constraints Commands that define a database, including creating, altering, and dropping tables and establishing constraints Data Manipulation Language (DML) Data Manipulation Language (DML) Commands that maintain and query a database Commands that maintain and query a database Data Control Language (DCL) Data Control Language (DCL) Commands that control a database, including administering privileges and committing data Commands that control a database, including administering privileges and committing data

7. Chapter 7 © 2007 by Prentice Hall 7 Figure 7-1 A simplified schematic of a typical SQL environment, as described by the SQL-2003 standard

8. Chapter 7 © 2007 by Prentice Hall 8 Some SQL Data types

9. Chapter 7 © 2007 by Prentice Hall 9 Figure 7-4 DDL, DML, DCL, and the database development process

10. Chapter 7 © 2007 by Prentice Hall 10 SQL Database Definition Data Definition Language (DDL) Data Definition Language (DDL) Major CREATE statements: Major CREATE statements: CREATE SCHEMA–defines a portion of the database owned by a particular user CREATE SCHEMA–defines a portion of the database owned by a particular user CREATE TABLE–defines a table and its columns CREATE TABLE–defines a table and its columns CREATE VIEW–defines a logical table from one or more views CREATE VIEW–defines a logical table from one or more views Other CREATE statements: CHARACTER SET, COLLATION, TRANSLATION, ASSERTION, DOMAIN Other CREATE statements: CHARACTER SET, COLLATION, TRANSLATION, ASSERTION, DOMAIN

11. Chapter 7 © 2007 by Prentice Hall 11 Table Creation Figure 7-5 General syntax for CREATE TABLE Steps in table creation: 1.Identify data types for attributes 2.Identify columns that can and cannot be null 3.Identify columns that must be unique (candidate keys) 4.Identify primary key – foreign key mates 5.Determine default values 6.Identify constraints on columns (domain specifications) 7.Create the table and associated indexes

12. Chapter 7 © 2007 by Prentice Hall 12 The following slides create tables for this enterprise data model

13. Chapter 7 © 2007 by Prentice Hall 13 Figure 7-6 SQL database definition commands for Pine Valley Furniture Overall table definitions

14. Chapter 7 © 2007 by Prentice Hall 14 Defining attributes and their data types

15. Chapter 7 © 2007 by Prentice Hall 15 Non-nullable specification Identifying primary key Primary keys can never have NULL values

16. Chapter 7 © 2007 by Prentice Hall 16 Non-nullable specifications Primary key Some primary keys are composite– composed of multiple attributes

17. Chapter 7 © 2007 by Prentice Hall 17 Default value Domain constraint Controlling the values in attributes

18. Chapter 7 © 2007 by Prentice Hall 18 Primary key of parent table Identifying foreign keys and establishing relationships Foreign key of dependent table

19. Chapter 7 © 2007 by Prentice Hall 19 Data Integrity Controls Referential integrity–constraint that ensures that foreign key values of a table must match primary key values of a related table in 1:M relationships Referential integrity–constraint that ensures that foreign key values of a table must match primary key values of a related table in 1:M relationships Restricting: Restricting: Deletes of primary records Deletes of primary records Updates of primary records Updates of primary records Inserts of dependent records Inserts of dependent records

20. Chapter 7 © 2007 by Prentice Hall 20 Relational integrity is enforced via the primary- key to foreign- key match Figure 7-7 Ensuring data integrity through updates

21. Chapter 7 © 2007 by Prentice Hall 21 Changing and Removing Tables ALTER TABLE statement allows you to change column specifications: ALTER TABLE statement allows you to change column specifications: ALTER TABLE CUSTOMER_T ADD (TYPE VARCHAR(2)) ALTER TABLE CUSTOMER_T ADD (TYPE VARCHAR(2)) DROP TABLE statement allows you to remove tables from your schema: DROP TABLE statement allows you to remove tables from your schema: DROP TABLE CUSTOMER_T DROP TABLE CUSTOMER_T

22. Chapter 7 © 2007 by Prentice Hall 22 Schema Definition Control processing/storage efficiency: Control processing/storage efficiency: Choice of indexes Choice of indexes File organizations for base tables File organizations for base tables File organizations for indexes File organizations for indexes Data clustering Data clustering Statistics maintenance Statistics maintenance Creating indexes Creating indexes Speed up random/sequential access to base table data Speed up random/sequential access to base table data Example Example CREATE INDEX NAME_IDX ON CUSTOMER_T(CUSTOMER_NAME) CREATE INDEX NAME_IDX ON CUSTOMER_T(CUSTOMER_NAME) This makes an index for the CUSTOMER_NAME field of the CUSTOMER_T table This makes an index for the CUSTOMER_NAME field of the CUSTOMER_T table

23. Chapter 7 © 2007 by Prentice Hall 23 Insert Statement Adds data to a table Adds data to a table Inserting into a table Inserting into a table INSERT INTO CUSTOMER_T VALUES (001, ‘Contemporary Casuals’, ‘1355 S. Himes Blvd.’, ‘Gainesville’, ‘FL’, 32601); INSERT INTO CUSTOMER_T VALUES (001, ‘Contemporary Casuals’, ‘1355 S. Himes Blvd.’, ‘Gainesville’, ‘FL’, 32601); Inserting a record that has some null attributes requires identifying the fields that actually get data Inserting a record that has some null attributes requires identifying the fields that actually get data INSERT INTO PRODUCT_T (PRODUCT_ID, PRODUCT_DESCRIPTION,PRODUCT_FINISH, STANDARD_PRICE, PRODUCT_ON_HAND) VALUES (1, ‘End Table’, ‘Cherry’, 175, 8); INSERT INTO PRODUCT_T (PRODUCT_ID, PRODUCT_DESCRIPTION,PRODUCT_FINISH, STANDARD_PRICE, PRODUCT_ON_HAND) VALUES (1, ‘End Table’, ‘Cherry’, 175, 8); Inserting from another table Inserting from another table INSERT INTO CA_CUSTOMER_T SELECT * FROM CUSTOMER_T WHERE STATE = ‘CA’; INSERT INTO CA_CUSTOMER_T SELECT * FROM CUSTOMER_T WHERE STATE = ‘CA’;

24. Chapter 7 © 2007 by Prentice Hall 24 Creating Tables with Identity Columns Inserting into a table does not require explicit customer ID entry or field list INSERT INTO CUSTOMER_T VALUES ( ‘Contemporary Casuals’, ‘1355 S. Himes Blvd.’, ‘Gainesville’, ‘FL’, 32601); New with SQL:2003

25. Chapter 7 © 2007 by Prentice Hall 25 Delete Statement Removes rows from a table Removes rows from a table Delete certain rows Delete certain rows DELETE FROM CUSTOMER_T WHERE STATE = ‘HI’; DELETE FROM CUSTOMER_T WHERE STATE = ‘HI’; Delete all rows Delete all rows DELETE FROM CUSTOMER_T; DELETE FROM CUSTOMER_T;

26. Chapter 7 © 2007 by Prentice Hall 26 Update Statement Modifies data in existing rows Modifies data in existing rows UPDATE PRODUCT_T SET UNIT_PRICE = 775 WHERE PRODUCT_ID = 7; UPDATE PRODUCT_T SET UNIT_PRICE = 775 WHERE PRODUCT_ID = 7;

27. Chapter 7 © 2007 by Prentice Hall 27 Merge Statement Makes it easier to update a table…allows combination of Insert and Update in one statement Useful for updating master tables with new data