Database Management Systems SQL And DDL language

These are the slides for database systems

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 SELECTstatements
•Execute a basic SELECTstatement
•Differentiate between SQL statements and
iSQL*Plus commands

3. 1-3 Copyright © Oracle Corporation, 2001. All rights reserved.
Capabilities of SQL SELECTStatements
SelectionProjection
Table 1 Table 2
Table 1Table 1
Join

4. 1-4 Copyright © Oracle Corporation, 2001. All rights reserved.
Basic SELECTStatement
SELECT *|{[DISTINCT] column|expression[alias],...}
FROM table;
•SELECTidentifies whatcolumns
•FROMidentifies whichtable

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
•iSQL*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 ASkeyword 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
SELECT last_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 SELECTlist.
•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;
…

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

24. 1-24 Copyright © Oracle Corporation, 2001. All rights reserved.
SQL and iSQL*Plus Interaction
SQL statements
Oracle
server
Query resultsiSQL*Plus
commands
Client
Formatted report
Internet
Browser
iSQL*Plus

25. 1-25 Copyright © Oracle Corporation, 2001. All rights reserved.
SQL Statements Versus
iSQL*Plus Commands
SQL
statements
SQL
•A language
•ANSI standard
•Keyword cannot be
abbreviated
•Statements manipulate
data and table definitions
in the database
iSQL*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
iSQL*Plus
commands

26. 1-26 Copyright © Oracle Corporation, 2001. All rights reserved.
Overview of iSQL*Plus
After you log into iSQL*Plus, you can:
•Describe the table structure
•Edit your SQL statement
•Execute SQL from iSQL*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 iSQL*Plus
Edit window

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

28. 1-28 Copyright © Oracle Corporation, 2001. All rights reserved.
The iSQL*Plus Environment
3 4 5
6
1
2
8910

29. 1-29 Copyright © Oracle Corporation, 2001. All rights reserved.
Displaying Table Structure
Use the iSQL*Plus DESCRIBEcommand 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; 1
2

32. 1-32 Copyright © Oracle Corporation, 2001. All rights reserved.
Interacting with Script Files
1
D:\temp\emp_sql.htm
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;
1
23

34. 1-34 Copyright © Oracle Corporation, 2001. All rights reserved.
Summary
SELECT *|{[DISTINCT] column|expression [alias],...}
FROM table;
In this lesson, you should have learned how to:
•Write a SELECTstatement 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 iSQL*Plus environment to write, save, and
execute SQL statements and iSQL*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 iSQL*Plus