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

© 2007 by Prentice Hall© 2007 by Prentice Hall(Hoffer, Prescott & McFadden)(Hoffer, Prescott & McFadden) 11

Introduction to SQLIntroduction to SQL

Chapter 7 © 2007 by Prentice Hall© 2007 by Prentice Hall 22

SQL OverviewSQL Overview Structured Query LanguageStructured Query Language

The standard for relational database The standard for relational database management systems (RDBMS) management systems (RDBMS)

RDBMS: A database management RDBMS: A database management system that manages data as a system that manages data as a collection of tables in which all collection of tables in which all relationships are represented by relationships are represented by common values in related tablescommon values in related tables


History of SQLHistory of SQL 1970–E. Codd develops relational database 1970–E. Codd develops relational database

conceptconcept 1974-1979–System R with Sequel (later SQL) 1974-1979–System R with Sequel (later SQL)

created at IBM Research Labcreated at IBM Research Lab 1979–Oracle markets first relational DB with SQL1979–Oracle markets first relational DB with SQL 1986–ANSI SQL standard released1986–ANSI SQL standard released 1989, 1992, 1999, 2003–Major ANSI standard 1989, 1992, 1999, 2003–Major ANSI standard

updatesupdates Current–SQL is supported by most major Current–SQL is supported by most major

database vendorsdatabase vendors


Purpose of SQL StandardPurpose of SQL Standard Specify syntax/semantics for data Specify syntax/semantics for data

definition and manipulationdefinition and manipulation Define data structuresDefine data structures Enable portabilityEnable portability Specify minimal (level 1) and complete Specify minimal (level 1) and complete

(level 2) standards(level 2) standards Allow for later growth/enhancement to Allow for later growth/enhancement to

standardstandard


Benefits of a Standardized Benefits of a Standardized Relational LanguageRelational Language

Reduced training costsReduced training costs ProductivityProductivity Application portabilityApplication portability Application longevityApplication longevity Reduced dependence on a single Reduced dependence on a single

vendorvendor Cross-system communicationCross-system communication


SQL EnvironmentSQL Environment CatalogCatalog

A set of schemas that constitute the description of a databaseA set of schemas that constitute the description of a database SchemaSchema

The structure that contains descriptions of objects created by a The structure that contains descriptions of objects created by a user (base tables, views, constraints)user (base tables, views, constraints)

Data Definition Language (DDL)Data Definition Language (DDL) Commands that define a database, including creating, altering, Commands that define a database, including creating, altering,

and dropping tables and establishing constraintsand dropping tables and establishing constraints Data Manipulation Language (DML)Data Manipulation Language (DML)

Commands that maintain and query a databaseCommands that maintain and query a database Data Control Language (DCL)Data Control Language (DCL)

Commands that control a database, including administering Commands that control a database, including administering privileges and committing dataprivileges and committing data


Figure 7-1A simplified schematic of a typical SQL environment, as described by the SQL-2003 standard


Some SQL Data types Some SQL Data types


Figure 7-4 DDL, DML, DCL, and the database development process


SQL Database DefinitionSQL Database Definition Data Definition Language (DDL)Data Definition Language (DDL) Major CREATE statements:Major CREATE statements:

CREATE SCHEMA–defines a portion of the CREATE SCHEMA–defines a portion of the database owned by a particular userdatabase owned by a particular user

CREATE TABLE–defines a table and its CREATE TABLE–defines a table and its columnscolumns

CREATE VIEW–defines a logical table from CREATE VIEW–defines a logical table from one or more viewsone or more views

Other CREATE statements: CHARACTER Other CREATE statements: CHARACTER SET, COLLATION, TRANSLATION, SET, COLLATION, TRANSLATION, ASSERTION, DOMAINASSERTION, DOMAIN


Table CreationTable CreationFigure 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


The following slides create tables The following slides create tables for this enterprise data modelfor this enterprise data model


Figure 7-6 SQL database definition commands for Pine Valley Furniture

Overall table definitions


Defining attributes and their data types


Non-nullable specification

Identifying primary key

Primary keys can never have NULL values


Non-nullable specifications

Primary key

Some primary keys are composite– composed of multiple attributes


Default value

Domain constraint

Controlling the values in attributes


Primary key of parent table

Identifying foreign keys and establishing relationships

Foreign key of dependent table


Data Integrity ControlsData Integrity Controls Referential integrity–constraint Referential integrity–constraint

that ensures that foreign key that ensures that foreign key values of a table must match values of a table must match primary key values of a related primary key values of a related table in 1:M relationshipstable in 1:M relationships

Restricting:Restricting: Deletes of primary recordsDeletes of primary records Updates of primary recordsUpdates of primary records Inserts of dependent recordsInserts of dependent records


Relational integrity is enforced via the primary-key to foreign-key match

Figure 7-7 Ensuring data integrity through updates


Changing and Removing Changing and Removing TablesTables

ALTER TABLE statement allows you ALTER TABLE statement allows you to change column specifications:to change column specifications: ALTER TABLE CUSTOMER_T ADD (TYPE ALTER TABLE CUSTOMER_T ADD (TYPE

VARCHAR(2))VARCHAR(2)) DROP TABLE statement allows you to DROP TABLE statement allows you to

remove tables from your schema:remove tables from your schema: DROP TABLE CUSTOMER_TDROP TABLE CUSTOMER_T


Schema DefinitionSchema Definition Control processing/storage efficiency:Control processing/storage efficiency:

Choice of indexesChoice of indexes File organizations for base tablesFile organizations for base tables File organizations for indexesFile organizations for indexes Data clusteringData clustering Statistics maintenanceStatistics maintenance

Creating indexesCreating indexes Speed up random/sequential access to base table dataSpeed up random/sequential access to base table data ExampleExample

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 This makes an index for the CUSTOMER_NAME field of the

CUSTOMER_T tableCUSTOMER_T table


Insert StatementInsert Statement Adds data to a tableAdds data to a table Inserting into a tableInserting into a table

INSERT INTO CUSTOMER_T VALUES (001, ‘Contemporary INSERT INTO CUSTOMER_T VALUES (001, ‘Contemporary Casuals’, ‘1355 S. Himes Blvd.’, ‘Gainesville’, ‘FL’, Casuals’, ‘1355 S. Himes Blvd.’, ‘Gainesville’, ‘FL’, 32601);32601);

Inserting a record that has some null attributes Inserting a record that has some null attributes requires identifying the fields that actually get requires identifying the fields that actually get datadata INSERT INTO PRODUCT_T (PRODUCT_ID, INSERT INTO PRODUCT_T (PRODUCT_ID,

PRODUCT_DESCRIPTION,PRODUCT_FINISH, STANDARD_PRICE, PRODUCT_DESCRIPTION,PRODUCT_FINISH, STANDARD_PRICE, PRODUCT_ON_HAND) VALUES (1, ‘End Table’, ‘Cherry’, 175, 8);PRODUCT_ON_HAND) VALUES (1, ‘End Table’, ‘Cherry’, 175, 8);

Inserting from another tableInserting from another table INSERT INTO CA_CUSTOMER_T SELECT * FROM CUSTOMER_T INSERT INTO CA_CUSTOMER_T SELECT * FROM CUSTOMER_T

WHERE STATE = ‘CA’;WHERE STATE = ‘CA’;


Creating Tables with Identity Creating Tables with Identity ColumnsColumns

Inserting into a table does not require explicit customer ID Inserting into a table does not require explicit customer ID entry or field listentry or field list

INSERT INTO CUSTOMER_T VALUES ( ‘Contemporary INSERT INTO CUSTOMER_T VALUES ( ‘Contemporary Casuals’, ‘1355 S. Himes Blvd.’, ‘Gainesville’, ‘FL’, 32601);Casuals’, ‘1355 S. Himes Blvd.’, ‘Gainesville’, ‘FL’, 32601);

New with SQL:2003


Delete StatementDelete Statement

Removes rows from a tableRemoves rows from a table Delete certain rowsDelete certain rows

DELETE FROM CUSTOMER_T WHERE DELETE FROM CUSTOMER_T WHERE STATE = ‘HI’;STATE = ‘HI’;

Delete all rowsDelete all rows DELETE FROM CUSTOMER_T;DELETE FROM CUSTOMER_T;


Update StatementUpdate Statement

Modifies data in existing rowsModifies data in existing rows

UPDATE PRODUCT_T SET UNIT_PRICE = UPDATE PRODUCT_T SET UNIT_PRICE = 775 WHERE PRODUCT_ID = 7;775 WHERE PRODUCT_ID = 7;


Merge StatementMerge 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

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