Copyright © 2004, Oracle. All rights reserved.

Lecture 4: Lecture 4: 1-Retrieving Data Using 1-Retrieving Data Using the SQL the SQL SELECTSELECT Statement Statement 2-Restricting and Sorting 2-Restricting and Sorting

DataData

ORACLEORACLE

ObjectivesObjectives

After completing this lesson, you should be able to do the following:◦List the capabilities of SQL SELECT

statements◦Execute a basic SELECT statement

Capabilities of SQL Capabilities of SQL SELECTSELECT StatementsStatements

SelectionProjection

Table 1 Table 2

Table 1Table 1

Join

Basic Basic SELECTSELECT Statement Statement

◦ SELECT identifies the columns to be displayed◦ FROM identifies the table containing those columns

SELECT *|{[DISTINCT] column|expression [alias],...}FROM table;

Selecting All ColumnsSelecting All Columns

SELECT *FROM departments;

Selecting Specific Selecting Specific ColumnsColumns

SELECT department_id, location_idFROM departments;

Writing SQL StatementsWriting 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.◦In SQL*plus, you are required to end

each SQL statement with a semicolon (;).

Arithmetic ExpressionsArithmetic Expressions

Create expressions with number and date data by using arithmetic operators.

OperatorDescription

+Add

-Subtract

*Multiply

/Divide

SELECT last_name, salary, salary + 300FROM employees;

Using Arithmetic Using Arithmetic OperatorsOperators

…

SELECT last_name, salary, 12*salary+100FROM employees;

Operator PrecedenceOperator Precedence

SELECT last_name, salary, 12*(salary+100)FROM employees;

…

…

1

2

Defining a Null ValueDefining a Null Value

◦ A null is a value that is unavailable, unassigned, unknown, or inapplicable.

◦ A null is not the same as a zero or a blank space.

SELECT last_name, job_id, salary, commission_pctFROM employees;

…

…

SELECT last_name, 12*salary*commission_pctFROM employees;

Null Values Null Values in Arithmetic Expressionsin Arithmetic Expressions

Arithmetic expressions containing a null value evaluate to null.

…

…

Defining a Column AliasDefining 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 if it is case-sensitive

Using Column AliasesUsing Column Aliases

SELECT last_name "Name" , salary*12 "Annual Salary"FROM employees;

SELECT last_name AS name, commission_pct commFROM employees;

…

…

Concatenation OperatorConcatenation Operator

A concatenation operator:◦ Links columns or character strings to

other columns ◦ Is represented by two vertical bars (||)◦ Creates a resultant column that is a

character expression

SELECT last_name||job_id AS "Employees"FROM employees;

…

Literal Character StringsLiteral Character Strings

◦A literal is a character, a number, or a date that is included in the SELECT statement.

◦Date and character literal values must be enclosed by single quotation marks.

◦Each character string is output once for eachrow returned.

Using Literal Character Using Literal Character StringsStrings

…

SELECT last_name ||' is a '||job_id AS "Employee Details"FROM employees;

Alternative Quote (Alternative Quote (qq) ) OperatorOperator◦Specify your own quotation mark

delimiter◦Choose any delimiter◦Increase readability and usabilitySELECT department_name ||

q'[, it's assigned Manager Id: ]' || manager_id AS "Department and Manager" FROM departments;

…

Duplicate RowsDuplicate Rows

The default display of queries is all rows, including duplicate rows.

SELECT department_idFROM employees;

…

SELECT DISTINCT department_idFROM employees;

…

1

2

SummarySummary

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 display more

descriptive column headings

SELECT *|{[DISTINCT] column|expression [alias],...}FROM table;

Practice 1Practice 1::1- The following SELECT statement executes successfully:

SELECT last_name, job_id, salary AS Sal

FROM employees;

True/False

2-The following SELECT statement executes successfully:

SELECT *

FROM job_grades;

True/False

3-There are four coding errors in the following statement. Can you identify them?

SELECT employee_id, last_name

sal x 12 ANNUAL SALARY

FROM employees;

Practice 1Practice 1: :

4-The HR department needs a query to display all unique job codes from the EMPLOYEES table.

5-The HR department has requested a report of all employees and their job IDs. Display the last name concatenated with the job ID (separated by a comma and space) and name the column Employee and Title.

Copyright © 2004, Oracle. All rights reserved.

22--Restricting and Sorting Restricting and Sorting

DataData

ORACLEORACLE

ObjectivesObjectives

After completing this lesson, you should be able to do the following:◦Limit the rows that are retrieved by a

query◦Sort the rows that are retrieved by a query

Limiting Rows Using a Limiting Rows Using a SelectionSelection

“retrieve allemployees in department 90”

EMPLOYEES

…

Limiting the Rows That Are Limiting the Rows That Are SelectedSelected

◦ Restrict the rows that are returned by using the WHERE clause:

◦ The WHERE clause follows the FROM clause.

SELECT *|{[DISTINCT] column | expression [alias],...}FROM table[WHERE condition(s)];

SELECT employee_id, last_name, job_id, department_idFROM employeesWHERE department_id = 90 ;

Using the Using the WHEREWHERE Clause Clause

SELECT last_name, job_id, department_idFROM employeesWHERE last_name = 'Whalen' ;

Character Strings and Character Strings and DatesDates

◦Character strings and date values are enclosed by single quotation marks.

◦Character values are case-sensitive, and date values are format-sensitive.

◦The default date format is DD-MON-RR.

Comparison ConditionsComparison Conditions

OperatorMeaning

=Equal to

>Greater than

>=Greater than or equal to

<Less than

<=Less than or equal to

<>Not equal to

BETWEEN...AND...

Between two values (inclusive)

IN(set)Match any of a list of values

LIKEMatch a character pattern

IS NULLIs a null value

SELECT last_name, salaryFROM employeesWHERE salary <= 3000 ;

Using Comparison Using Comparison ConditionsConditions

SELECT last_name, salaryFROM employeesWHERE salary BETWEEN 2500 AND 3500 ;

Using the Using the BETWEENBETWEEN ConditionCondition

Use the BETWEEN condition to display rows based on a range of values:

Lower limit Upper limit

SELECT employee_id, last_name, salary, manager_idFROM employeesWHERE manager_id IN (100, 101, 201) ;

Using the Using the ININ Condition Condition

Use the IN membership condition to test for values in a list:

SELECT first_nameFROM employeesWHERE first_name LIKE 'S%' ;

Using the Using the LIKELIKE Condition Condition

◦Use the LIKE condition to perform wildcard searches of valid search string values.

◦Search conditions can contain either literal characters or numbers: % denotes zero or many characters. _ denotes one character.

Using the Using the LIKELIKE Condition Condition◦You can combine pattern-matching

characters:SELECT last_nameFROM employeesWHERE last_name LIKE '_o%' ;

SELECT last_name, manager_idFROM employeesWHERE manager_id IS NULL ;

Using the Using the NULLNULL Conditions Conditions

Test for nulls with the IS NULL operator.

Logical ConditionsLogical Conditions

OperatorMeaning

ANDReturns TRUE if both component conditions are true

ORReturns TRUE if either component condition is true

NOTReturns TRUE if the following condition is false

SELECT employee_id, last_name, job_id, salaryFROM employeesWHERE salary >=10000AND job_id LIKE '%MAN%' ;

Using the Using the ANDAND Operator Operator

AND requires both conditions to be true:

SELECT employee_id, last_name, job_id, salaryFROM employeesWHERE salary >= 10000OR job_id LIKE '%MAN%' ;

Using the Using the OROR Operator Operator

OR requires either condition to be true:

SELECT last_name, job_idFROM employeesWHERE job_id NOT IN ('IT_PROG', 'ST_CLERK', 'SA_REP') ;

Using the Using the NOTNOT Operator Operator

Rules of PrecedenceRules of Precedence

You can use parentheses to override rules of precedence.

OperatorMeaning

1Arithmetic operators

2Concatenation operator

3Comparison conditions

4IS [NOT] NULL, LIKE, [NOT] IN

5[NOT] BETWEEN

6Not equal to

7NOT logical condition

8AND logical condition

9OR logical condition

SELECT last_name, job_id, salaryFROM employeesWHERE job_id = 'SA_REP'OR job_id = 'AD_PRES'AND salary > 15000;

Rules of PrecedenceRules of Precedence

SELECT last_name, job_id, salaryFROM employeesWHERE (job_id = 'SA_REP'OR job_id = 'AD_PRES')AND salary > 15000;

1

2

Using the Using the ORDER BYORDER BY ClauseClause◦Sort retrieved rows with the ORDER BY

clause: ASC: ascending order, default DESC: descending order

◦The ORDER BY clause comes last in the SELECT statement:

SELECT last_name, job_id, department_id, hire_dateFROM employeesORDER BY hire_date ;

…

SortingSorting

◦ Sorting in descending order:

◦ Sorting by column alias:

◦ Sorting by multiple columns:

SELECT last_name, job_id, department_id, hire_dateFROM employeesORDER BY hire_date DESC ;

1

SELECT employee_id, last_name, salary*12 annsalFROM employeesORDER BY annsal ;

2

SELECT last_name, department_id, salaryFROM employeesORDER BY department_id, salary DESC;

3

SELECT *|{[DISTINCT] column|expression [alias],...}FROM table[WHERE condition(s)][ORDER BY {column, expr, alias} [ASC|DESC]] ;

SummarySummary

In this lesson, you should have learned how to: ◦ Use the WHERE clause to restrict rows of output:

Use the comparison conditions Use the BETWEEN, IN, LIKE, and NULL conditions Apply the logical AND, OR, and NOT operators

◦ Use the ORDER BY clause to sort rows of output

Practice 2Practice 2::

1-The HR departments needs to find high-salary and low-salary employees. display the last name and salary of employees who earn between $5,000 and $12,000 and are in department 20 or 50. Label the columns Employee and Monthly Salary, respectively.

2- Create a report to display the last name, salary, and commission of all employees who earn commissions. Sort data in descending order of salary and commissions.

3- Display the last name of all employees who have both an a and an e in their last name.

4- Display the last name, job, and salary for all employees whose job is SA_REP or ST_CLERKand whose salary is not equal to $2,500, $3,500, or $7,000.