1. A Guide to SQL, Eighth Edition Chapter Three Creating Tables

2. A Guide to SQL, Eighth Edition 2 Objectives Create and run SQL commands Create tables Identify and use data types to define columns in tables Understand and use nulls Add rows to tables

3. A Guide to SQL, Eighth Edition 3 Objectives (continued) View table data Correct errors in a table Save SQL commands to a file Describe a table’s layout using SQL

4. A Guide to SQL, Eighth Edition 4 Introduction Structured Query Language (SQL) –Most popular and widely used language for retrieving and manipulating database data –Developed in mid 1970s under the name SEQUEL –Renamed SQL in 1980 –Used by most DBMSs

5. A Guide to SQL, Eighth Edition 5 Creating and Running SQL Commands Oracle Database 10g Express –Software used in text to illustrate SQL –Commands will work the same in other versions of Oracle Differences between Oracle and Microsoft Access and SQL Server 2005 are noted in special boxes

6. A Guide to SQL, Eighth Edition 6 Starting the Oracle Database Express Edition Software loads in Internet Explorer –Other browsers may not fully support examples used in text Must have a username and password Click icons on Home page to access various tools

7. A Guide to SQL, Eighth Edition 7 Starting the Oracle Database Express Edition (continued)

8. A Guide to SQL, Eighth Edition 8 Entering Commands

9. A Guide to SQL, Eighth Edition 9 Entering Commands (continued)

10. A Guide to SQL, Eighth Edition 10 Creating a Table Describe the layout of each table in the database Use CREATE TABLE command TABLE is followed by the table name Follow this with the names and data types of the columns in the table Data types define type and size of data

11. A Guide to SQL, Eighth Edition 11 Creating a Table (continued) Table and column name restrictions –Names cannot exceed 30 characters –Must start with a letter –Can contain letters, numbers, and underscores (_) –Cannot contain spaces

12. A Guide to SQL, Eighth Edition 12 Creating a Table (continued)

13. A Guide to SQL, Eighth Edition 13 Creating a Table (continued) Commands are free-format; no rules stating specific words in specific positions Indicate the end of a command by typing a semicolon Commands are not case sensitive In Oracle, enter the command in the SQL editor pane

14. A Guide to SQL, Eighth Edition 14 Creating a Table (continued)

15. A Guide to SQL, Eighth Edition 15 Creating a Table (continued)

16. A Guide to SQL, Eighth Edition 16 Creating a Table (continued)

17. A Guide to SQL, Eighth Edition 17 Correcting Errors in SQL Commands Use the same techniques that you might use in a word processor Make changes and click Run button to execute command again Check Results pane to determine if command executed successfully

18. A Guide to SQL, Eighth Edition 18 Dropping a Table Can correct errors by dropping (deleting) a table and starting over Useful when table is created before errors are discovered Command is followed by the table to be dropped and a semicolon Any data in table also deleted

19. A Guide to SQL, Eighth Edition 19 Using Data Types For each column, the type of data must be defined Common data types –CHAR(n) –VARCHAR(n) –DATE –DECIMAL(p,q) –INT – SMALLINT

20. A Guide to SQL, Eighth Edition 20 Using Nulls A special value to represent a situation when the actual value is not known for a column Can specify whether to allow nulls in the individual columns Should not allow nulls for primary key columns

21. A Guide to SQL, Eighth Edition 21 Using Nulls (continued) Use NOT NULL clause in CREATE TABLE command to exclude the use of nulls in a column Default is to allow null values If a column is defined as NOT NULL, system will reject any attempt to store a null value there

22. A Guide to SQL, Eighth Edition 22 Using Nulls (continued) CREATE TABLE REP (REP_NUM CHAR(2) PRIMARY KEY, LAST_NAME CHAR(15) NOT NULL, FIRST_NAME CHAR(15) NOT NULL, STREET CHAR(15), CITY CHAR(15), STATE CHAR(2), ZIP CHAR(5), COMMISSION DECIMAL(7,2), RATE DECIMAL(3,2) );

23. A Guide to SQL, Eighth Edition 23 Adding Rows to a Table INSERT Command –INSERT INTO followed by table name –VALUES command followed by specific values in parentheses –Values for character columns in single quotation marks

24. A Guide to SQL, Eighth Edition 24 The Insert Command

25. A Guide to SQL, Eighth Edition 25 The INSERT Command (continued) To add new rows, modify previous insert command Use same editing techniques as those used to correct errors

26. A Guide to SQL, Eighth Edition 26 Inserting a Row that Contains Nulls Use a special format of INSERT command to enter a null value in a table Identify the names of the columns that accept non-null values and then list only the non-null values after the VALUES command

27. A Guide to SQL, Eighth Edition 27 Inserting a Row that Contains Nulls (continued)

28. A Guide to SQL, Eighth Edition 28 Viewing Table Data Use SELECT command –Can display all the rows and columns in a table SELECT * FROM followed by the name of the table Ends with a semicolon

29. A Guide to SQL, Eighth Edition 29 Viewing Table Data (continued)

30. A Guide to SQL, Eighth Edition 30 Viewing Table Data (continued) In Access –Enter SELECT statement in SQL view In SQL Server –Enter SELECT statement in Query Editor window

31. A Guide to SQL, Eighth Edition 31 Correcting Errors in a Table UPDATE command is used to update a value in a table DELETE command allows you to delete a record INSERT command allows you to add a record

32. A Guide to SQL, Eighth Edition 32 Correcting Errors in a Table (continued)

33. A Guide to SQL, Eighth Edition 33 Correcting Errors in a Table (continued)

34. A Guide to SQL, Eighth Edition 34 Correcting Errors in a Table (continued)

35. A Guide to SQL, Eighth Edition 35 Saving SQL Commands Allows you to use commands again without retyping Save commands in a script file or script –Text file with.sql extension Script repository –Special location in Oracle –Can download to local drive

36. A Guide to SQL, Eighth Edition 36 Saving SQL Commands (continued) To create a script file in Oracle: –Use Script Editor page –Enter a name for script –Type the command or commands to save in script –Save the script

37. A Guide to SQL, Eighth Edition 37 Saving SQL Commands (continued) Once a script file is created: –Can view, edit, or run –Can delete –Can download from script repository to local drive –Can upload from local drive to script repository

38. A Guide to SQL, Eighth Edition 38 Saving SQL Commands (continued) Access –Does not use script files –Save SQL commands as query objects SQL Server –Can create scripts –Can view, edit, run scripts –Can delete scripts

39. A Guide to SQL, Eighth Edition 39 Creating the Remaining Database Tables Execute appropriate CREATE TABLE and INSERT commands Save these commands as scripts Separate multiple commands in a script file with a semicolon Figures 3-25 through 3-32 give additional table information for Premiere Products

40. A Guide to SQL, Eighth Edition 40 Describing a Table DESCRIBE command (Oracle) Documenter tool (Access) Exec sp_columns command (SQL Server)

41. A Guide to SQL, Eighth Edition 41 Describing a Table (continued)

42. A Guide to SQL, Eighth Edition 42 Summary Use the CREATE TABLE command to create tables Use the DROP TABLE command to delete a table CHAR, VARCHAR, DATE, DECIMAL, INT, and SMALLINT data types –Access does not support DECIMAL –SQL Server uses DATETIME instead of DATE

43. A Guide to SQL, Eighth Edition 43 Summary (continued) Null value used when actual value for a column is unknown, unavailable, or not applicable Use NOT Null clause to identify columns that cannot have a null value Use INSERT command to add rows Use SELECT command to view data in a table

44. A Guide to SQL, Eighth Edition 44 Summary (continued) Use UPDATE command to change the value in a column Use DELETE command to delete a row Save SQL commands in a script file Use DESCRIBE command to display a table’s structure