1. 1 Copyright © Oracle Corporation, 2001. All rights reserved. Writing Basic SQL SELECT Statements

2. 1-2 Copyright © Oracle Corporation, 2001. All rights reserved. Objectives After completing this lesson, you should be able to do the following: List the capabilities of SQL SELECT statements Execute a basic SELECT statement Differentiate between SQL statements and i SQL*Plus commands

3. 1-3 Copyright © Oracle Corporation, 2001. All rights reserved. Capabilities of SQL SELECT Statements Selection Projection Table 1 Table 2 Table 1 Join

4. 1-4 Copyright © Oracle Corporation, 2001. All rights reserved. Basic SELECT Statement SELECT*|{[DISTINCT] column|expression [alias],...} FROMtable; SELECT*|{[DISTINCT] column|expression [alias],...} FROMtable; SELECT identifies what columns FROM identifies which table

5. 1-5 Copyright © Oracle Corporation, 2001. All rights reserved. SELECT * FROM departments; Selecting All Columns

6. 1-6 Copyright © Oracle Corporation, 2001. All rights reserved. Selecting Specific Columns SELECT department_id, location_id FROM departments;

7. 1-7 Copyright © Oracle Corporation, 2001. All rights reserved. Writing SQL Statements SQL statements are not case sensitive. SQL statements can be on one or more lines. Keywords cannot be abbreviated or split across lines. Clauses are usually placed on separate lines. Indents are used to enhance readability.

8. 1-8 Copyright © Oracle Corporation, 2001. All rights reserved. Column Heading Defaults i SQL*Plus: –Default heading justification: Center –Default heading display: Uppercase SQL*Plus: –Character and Date column headings are left- justified –Number column headings are right-justified –Default heading display: Uppercase

9. 1-9 Copyright © Oracle Corporation, 2001. All rights reserved. Arithmetic Expressions Create expressions with number and date data by using arithmetic operators. Operator + - * / Description Add Subtract Multiply Divide

10. 1-10 Copyright © Oracle Corporation, 2001. All rights reserved. Using Arithmetic Operators SELECT last_name, salary, salary + 300 FROM employees; …

11. 1-11 Copyright © Oracle Corporation, 2001. All rights reserved. Operator Precedence Multiplication and division take priority over addition and subtraction. Operators of the same priority are evaluated from left to right. Parentheses are used to force prioritized evaluation and to clarify statements. ** //++__

12. 1-12 Copyright © Oracle Corporation, 2001. All rights reserved. Operator Precedence SELECT last_name, salary, 12*salary+100 FROM employees; …

13. 1-13 Copyright © Oracle Corporation, 2001. All rights reserved. Using Parentheses SELECT last_name, salary, 12*(salary+100) FROM employees; …

14. 1-14 Copyright © Oracle Corporation, 2001. All rights reserved. Defining a Null Value A null is a value that is unavailable, unassigned, unknown, or inapplicable. A null is not the same as zero or a blank space. SELECT last_name, job_id, salary, commission_pct FROM employees; … …

15. 1-15 Copyright © Oracle Corporation, 2001. All rights reserved. SELECT last_name, 12*salary*commission_pct FROM employees; Null Values in Arithmetic Expressions Arithmetic expressions containing a null value evaluate to null. … …

16. 1-16 Copyright © Oracle Corporation, 2001. All rights reserved. Defining a Column Alias A column alias: Renames a column heading Is useful with calculations Immediately follows the column name - there can also be the optional AS keyword between the column name and alias Requires double quotation marks if it contains spaces or special characters or is case sensitive

17. 1-17 Copyright © Oracle Corporation, 2001. All rights reserved. Using Column Aliases SELECT last_name "Name", salary*12 "Annual Salary" FROM employees; SELECT last_name AS name, commission_pct comm FROM employees; … …

18. 1-18 Copyright © Oracle Corporation, 2001. All rights reserved. Concatenation Operator A concatenation operator: Concatenates columns or character strings to other columns Is represented by two vertical bars (||) Creates a resultant column that is a character expression

19. 1-19 Copyright © Oracle Corporation, 2001. All rights reserved. Using the Concatenation Operator SELECTlast_name||job_id AS "Employees" FROM employees; …

20. 1-20 Copyright © Oracle Corporation, 2001. All rights reserved. Literal Character Strings A literal is a character, a number, or a date included in the SELECT list. Date and character literal values must be enclosed within single quotation marks. Each character string is output once for each row returned.

21. 1-21 Copyright © Oracle Corporation, 2001. All rights reserved. Using Literal Character Strings SELECT last_name||' is a '||job_id AS "Employee Details" FROM employees; …

22. 1-22 Copyright © Oracle Corporation, 2001. All rights reserved. Duplicate Rows The default display of queries is all rows, including duplicate rows. SELECT department_id FROM employees; SELECT department_id FROM employees; …

23. 1-23 Copyright © Oracle Corporation, 2001. All rights reserved. Eliminating Duplicate Rows Eliminate duplicate rows by using the DISTINCT keyword in the SELECT clause. SELECT DISTINCT department_id FROM employees;

24. 1-24 Copyright © Oracle Corporation, 2001. All rights reserved. SQL and i SQL*Plus Interaction SQL statements Oracle server Query results i SQL*Plus commands Client Formatted report InternetBrowser i SQL*Plus

25. 1-25 Copyright © Oracle Corporation, 2001. All rights reserved. SQL Statements Versus i SQL*Plus Commands SQLstatements SQL A language ANSI standard Keyword cannot be abbreviated Statements manipulate data and table definitions in the database i SQL*Plus An environment Oracle proprietary Keywords can be abbreviated Commands do not allow manipulation of values in the database Runs on a browser Centrally loaded, does not have to be implemented on each machine i SQL*Plus commands

26. 1-26 Copyright © Oracle Corporation, 2001. All rights reserved. Overview of i SQL*Plus After you log into i SQL*Plus, you can: Describe the table structure Edit your SQL statement Execute SQL from i SQL*Plus Save SQL statements to files and append SQL statements to files Execute statements stored in saved files Load commands from a text file into the i SQL*Plus Edit window

27. 1-27 Copyright © Oracle Corporation, 2001. All rights reserved. Logging In to i SQL*Plus From your Windows browser environment:

28. 1-28 Copyright © Oracle Corporation, 2001. All rights reserved. The i SQL*Plus Environment 3456 7 128910

29. 1-29 Copyright © Oracle Corporation, 2001. All rights reserved. Displaying Table Structure Use the i SQL*Plus DESCRIBE command to display the structure of a table. DESC[RIBE] tablename

30. 1-30 Copyright © Oracle Corporation, 2001. All rights reserved. Displaying Table Structure DESCRIBE employees

31. 1-31 Copyright © Oracle Corporation, 2001. All rights reserved. Interacting with Script Files SELECT last_name, hire_date, salary FROM employees; 12

32. 1-32 Copyright © Oracle Corporation, 2001. All rights reserved. Interacting with Script Files 1 D:\temp\emp_sql.htm 2 SELECT last_name, hire_date, salary FROM employees; 3

33. 1-33 Copyright © Oracle Corporation, 2001. All rights reserved. Interacting with Script Files DESCRIBE employees SELECT first_name, last_name, job_id FROM employees; 123

34. 1-34 Copyright © Oracle Corporation, 2001. All rights reserved. Summary SELECT*|{[DISTINCT] column|expression [alias],...} FROMtable; SELECT*|{[DISTINCT] column|expression [alias],...} FROMtable; In this lesson, you should have learned how to: Write a SELECT statement that: –Returns all rows and columns from a table –Returns specified columns from a table –Uses column aliases to give descriptive column headings Use the i SQL*Plus environment to write, save, and execute SQL statements and i SQL*Plus commands.

35. 1-35 Copyright © Oracle Corporation, 2001. All rights reserved. Practice 1 Overview This practice covers the following topics: Selecting all data from different tables Describing the structure of tables Performing arithmetic calculations and specifying column names Using i SQL*Plus

36. 1-36 Copyright © Oracle Corporation, 2001. All rights reserved.

37. 1-37 Copyright © Oracle Corporation, 2001. All rights reserved.

38. 1-38 Copyright © Oracle Corporation, 2001. All rights reserved.

39. 1-39 Copyright © Oracle Corporation, 2001. All rights reserved.

40. 1-40 Copyright © Oracle Corporation, 2001. All rights reserved.