1. © 2011 Pearson Education 1 Chapter 6: Basic SQL Modern Database Management 10 th Edition, International Edition Jeffrey A. Hoffer, V. Ramesh, Heikki Topi

2. Chapter 6 © 2011 Pearson Education 2 Objectives Define terms Define terms Interpret history and role of SQL Interpret history and role of SQL Define a database using SQL data definition language Define a database using SQL data definition language Write single table queries using SQL Write single table queries using SQL Establish referential integrity using SQL Establish referential integrity using SQL Discuss SQL:1999 and SQL:200n standards Discuss SQL:1999 and SQL:200n standards

3. Chapter 6 © 2011 Pearson Education 3 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

4. Chapter 6 © 2011 Pearson Education 4 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

5. Chapter 6 © 2011 Pearson Education 5 Purpose of SQL Standard Specify syntax/semantics for data definition and manipulation Specify syntax/semantics for data definition and manipulation Define data structures and basic operations Define data structures and basic operations Enable portability of database definition and application modules Enable portability of database definition and application modules 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

6. Chapter 6 © 2011 Pearson Education 6 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

7. Chapter 6 © 2011 Pearson Education 7 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

8. Chapter 6 © 2011 Pearson Education 8 Figure 6-1 A simplified schematic of a typical SQL environment, as described by the SQL: 200n standard

9. Chapter 6 © 2011 Pearson Education 9 SQL Data Types

10. Chapter 6 © 2011 Pearson Education 10 Figure 6-4 DDL, DML, DCL, and the database development process

11. Chapter 6 © 2011 Pearson Education 11 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 new table and its columns CREATE TABLE–defines a new table and its columns CREATE VIEW–defines a logical table from one or more tables or views CREATE VIEW–defines a logical table from one or more tables or views Other CREATE statements: CHARACTER SET, COLLATION, TRANSLATION, ASSERTION, DOMAIN Other CREATE statements: CHARACTER SET, COLLATION, TRANSLATION, ASSERTION, DOMAIN

12. Chapter 6 © 2011 Pearson Education 12 Table Creation Figure 6-5 General syntax for CREATE TABLE statement used in data definition language 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

13. Chapter 6 © 2011 Pearson Education 13 The following slides create tables for this enterprise data model (from Chapter 1, Figure 1-3)

14. Chapter 6 © 2011 Pearson Education 14 Figure 6-6 SQL database definition commands for Pine Valley Furniture Company (Oracle 11g) Overall table definitions

15. Chapter 6 © 2011 Pearson Education 15 Defining attributes and their data types

16. Chapter 6 © 2011 Pearson Education 16 Non-nullable specification Identifying primary key Primary keys can never have NULL values

17. Chapter 6 © 2011 Pearson Education 17 Non-nullable specifications Primary key Some primary keys are composite– composed of multiple attributes

18. Chapter 6 © 2011 Pearson Education 18 Default value Domain constraint Controlling the values in attributes

19. Chapter 6 © 2011 Pearson Education 19 Primary key of parent table Identifying foreign keys and establishing relationships Foreign key of dependent table

20. Chapter 6 © 2011 Pearson Education 20 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

21. Chapter 6 © 2011 Pearson Education 21 Relational integrity is enforced via the primary- key to foreign- key match Figure 6-7 Ensuring data integrity through updates

22. Chapter 6 © 2011 Pearson Education 22 Changing Tables ALTER TABLE statement allows you to change column specifications: ALTER TABLE statement allows you to change column specifications: Table Actions: Table Actions: Example (adding a new column with a default value) : Example (adding a new column with a default value) :

23. Chapter 6 © 2011 Pearson Education ALTER TABLE 23 Adding Foreign key Adding Foreign key ALTER TABLE table_name ADD [CONSTRAINT constraint_name] FOREIGN KEY (col1, col2) REFERENCES table_2 (cola,colb); Adding a unique constraint Adding a unique constraint ALTER TABLE table_name ADD [CONSTRAINT constraint_name] UNIQUE (column_name);

24. Chapter 6 © 2011 Pearson Education ALTER TABLE Disabling/Enabling Constraints Disabling/Enabling Constraints ALTER TABLE table-name {DISABLE|ENABLE} Constraint-specification; ALTER TABLE table-name {DISABLE|ENABLE} CONSTRAINT constraint-name ; 24

25. Chapter 6 © 2011 Pearson Education ALTER TABLE Adding a new Column Adding a new Column ALTER TABLE some_table ADD column_name datatype; Renaming a column name Renaming a column name ALTER TABLE some_table RENAME COLUMN column_name TO new_column_name; Changing a column's type Changing a column's type ALTER TABLE some_table MODIFY (column_name datatype); 25

26. Chapter 6 © 2011 Pearson Education ALTER TABLE Changing null to not null or vice versa Changing null to not null or vice versa ALTER TABLE some_table MODIFY (column_name NOT NULL); ALTER TABLE some_table MODIFY (colimn_name NULL); Removing a constraint Removing a constraint ALTER TABLE table_name DROP CONSTRAINT constraint_name; 26

27. Chapter 6 © 2011 Pearson Education ALTER TABLE Rename table Rename table ALTER TABLE table_name_1 RENAME TO table_name_2; 27

28. Chapter 6 © 2011 Pearson Education 28 Removing Tables 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

29. Chapter 6 © 2011 Pearson Education 29 Insert Statement Adds one or more rows to a table Adds one or more rows to a table Inserting into a table Inserting into a table 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 Inserting from another table Inserting from another table

30. Chapter 6 © 2011 Pearson Education 30 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); Introduced with SQL:200n

31. Chapter 6 © 2011 Pearson Education 31 Delete Statement Removes rows from a table Removes rows from a table Delete certain rows Delete certain rows DELETE FROM CUSTOMER_T WHERE CUSTOMERSTATE = ‘HI’; DELETE FROM CUSTOMER_T WHERE CUSTOMERSTATE = ‘HI’; Delete all rows Delete all rows DELETE FROM CUSTOMER_T; DELETE FROM CUSTOMER_T;

32. Chapter 6 © 2011 Pearson Education 32 Update Statement Modifies data in existing rows Modifies data in existing rows

33. Chapter 6 © 2011 Pearson Education 33 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

34. Chapter 6 © 2011 Pearson Education 34 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(CUSTOMERNAME) CREATE INDEX NAME_IDX ON CUSTOMER_T(CUSTOMERNAME) This makes an index for the CUSTOMERNAME field of the CUSTOMER_T table This makes an index for the CUSTOMERNAME field of the CUSTOMER_T table

35. Chapter 6 © 2011 Pearson Education 35 SELECT Statement Used for queries on single or multiple tables Used for queries on single or multiple tables Clauses of the SELECT statement: Clauses of the SELECT statement: SELECT SELECT List the columns (and expressions) that should be returned from the query List the columns (and expressions) that should be returned from the query FROM FROM Indicate the table(s) or view(s) from which data will be obtained Indicate the table(s) or view(s) from which data will be obtained WHERE WHERE Indicate the conditions under which a row will be included in the result Indicate the conditions under which a row will be included in the result GROUP BY GROUP BY Indicate categorization of results Indicate categorization of results HAVING HAVING Indicate the conditions under which a category (group) will be included Indicate the conditions under which a category (group) will be included ORDER BY ORDER BY Sorts the result according to specified criteria Sorts the result according to specified criteria

36. Chapter 6 © 2011 Pearson Education 36 Figure 6-10 SQL statement processing order (adapted from van der Lans, 2006 p.100)

37. Chapter 6 © 2011 Pearson Education 37 SELECT Example Find products with standard price less than $275 Find products with standard price less than $275 Table 6-3: Comparison Operators in SQL

38. Chapter 6 © 2011 Pearson Education 38 SELECT Example Using Alias Alias is an alternative column or table name Alias is an alternative column or table name SELECT CUST.CUSTOMERNAME AS NAME, CUST.CUSTOMERADDRESS FROM CUSTOMER_V CUST WHERE NAME = ‘Home Furnishings’;

39. Chapter 6 © 2011 Pearson Education 39 SELECT Example Using a Function Using the COUNT aggregate function to find totals Using the COUNT aggregate function to find totals SELECT COUNT(*) FROM ORDERLINE_T WHERE ORDERID = 1004; Note: with aggregate functions you can’t have single-valued columns included in the SELECT clause, unless they are included in the GROUP BY clause

40. Chapter 6 © 2011 Pearson Education 40 SELECT Example–Boolean Operators AND, OR, and NOT Operators for customizing conditions in WHERE clause AND, OR, and NOT Operators for customizing conditions in WHERE clause Note: the LIKE operator allows you to compare strings using wildcards. For example, the % wildcard in ‘%Desk’ indicates that all strings that have any number of characters preceding the word “Desk” will be allowed.

41. Chapter 6 © 2011 Pearson Education 41 Figure 6-9 Boolean query without use of parentheses

42. Chapter 6 © 2011 Pearson Education 42 SELECT Example–Boolean Operators With parentheses…these override the normal precedence of Boolean operators With parentheses…these override the normal precedence of Boolean operators Note: by default, the AND operator takes precedence over the OR operator. With parentheses, you can make the OR take place before the AND.

43. Chapter 6 © 2011 Pearson Education 43 Figure 6-9 Boolean query with use of parentheses

44. Chapter 6 © 2011 Pearson Education 44 SELECT Example – Sorting Results with the ORDER BY Clause Sort the results first by STATE, and within a state by the CUSTOMER NAME Sort the results first by STATE, and within a state by the CUSTOMER NAME Note: the IN operator in this example allows you to include rows whose CustomerState value is either FL, TX, CA, or HI. It is more efficient than separate OR conditions.

45. Chapter 6 © 2011 Pearson Education 45 SELECT Example– Categorizing Results Using the GROUP BY Clause For use with aggregate functions For use with aggregate functions Scalar aggregate: single value returned from SQL query with aggregate function Scalar aggregate: single value returned from SQL query with aggregate function Vector aggregate: multiple values returned from SQL query with aggregate function (via GROUP BY) Vector aggregate: multiple values returned from SQL query with aggregate function (via GROUP BY) Note: you can use single-value fields with aggregate functions if they are included in the GROUP BY clause

46. Chapter 6 © 2011 Pearson Education 46 SELECT Example– Qualifying Results by Categories Using the HAVING Clause For use with GROUP BY For use with GROUP BY Like a WHERE clause, but it operates on groups (categories), not on individual rows. Here, only those groups with total numbers greater than 1 will be included in final result.

47. Chapter 6 © 2011 Pearson Education 47 Using and Defining Views Views provide users controlled access to tables Views provide users controlled access to tables Base Table–table containing the raw data Base Table–table containing the raw data Dynamic View Dynamic View A “virtual table” created dynamically upon request by a user A “virtual table” created dynamically upon request by a user No data actually stored; instead data from base table made available to user No data actually stored; instead data from base table made available to user Based on SQL SELECT statement on base tables or other views Based on SQL SELECT statement on base tables or other views Materialized View Materialized View Copy or replication of data Copy or replication of data Data actually stored Data actually stored Must be refreshed periodically to match the corresponding base tables Must be refreshed periodically to match the corresponding base tables

48. Chapter 6 © 2011 Pearson Education 48 Sample CREATE VIEW  View has a name  View is based on a SELECT statement  CHECK_OPTION works only for updateable views and prevents updates that would create rows not included in the view

49. Chapter 6 © 2011 Pearson Education 49 Advantages of Views Simplify query commands Simplify query commands Assist with data security (but don't rely on views for security, there are more important security measures) Assist with data security (but don't rely on views for security, there are more important security measures) Enhance programming productivity Enhance programming productivity Contain most current base table data Contain most current base table data Use little storage space Use little storage space Provide customized view for user Provide customized view for user Establish physical data independence Establish physical data independence

50. Chapter 6 © 2011 Pearson Education 50 Disadvantages of Views Use processing time each time view is referenced Use processing time each time view is referenced May or may not be directly updateable May or may not be directly updateable

51. Chapter 6 © 2011 Pearson Education 51 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America.