Oracle Lecture 4

7/29/2019 Oracle Lecture 4

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Copyright 2004, Oracle. All rights reserved.

Lecture 4:

1-Retrieving Data Usingthe SQL SELECT Statement

2-Restricting and Sorting Data

ORACLE


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Objectives

After completing this lesson, you should

be able to do the following:

List the capabilities of SQL SELECTstatements

Execute a basic SELECT statement


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Capabilities of SQL SELECT

Statements

SelectionProjection

Table 1 Table 2

Table 1Table 1

Join


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Basic SELECT Statement

SELECT identifies the columns to be displayed

FROM identifies the table containing thosecolumns

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

FROM table;


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Selecting All Columns

SELECT *

FROM departments;


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Selecting Specific Columns

SELECT department_id, location_id

FROM departments;


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Writing SQL Statements

SQL statements are not case-sensitive.

SQL statements can be on one or morelines.

Keywords cannot be abbreviated or splitacross lines.

Clauses are usually placed on separatelines.

Indents are used to enhance readability.

In SQL*plus, you are required to endeach SQL statement with a semicolon (;).


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Arithmetic Expressions

Create expressions with number and date data byusing arithmetic operators.

Operator Description

+ Add

- Subtract

* Multiply

/ Divide


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SELECT last_name, salary, salary + 300

FROM employees;

Using Arithmetic Operators


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SELECT last_name, salary, 12*salary+100

FROM employees;

Operator Precedence

SELECT last_name, salary, 12*(salary+100)

FROM employees;

1

2


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Defining 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 blankspace.

SELECT last_name, job_id, salary, commission_pctFROM employees;


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SELECT last_name, 12*salary*commission_pct

FROM employees;

Null Values

in Arithmetic Expressions

Arithmetic expressions containing a null value evaluateto null.


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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 keywordbetween the column name and alias.)

Requires double quotation marks if itcontains spaces or special characters or if it

is case-sensitive


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Using Column Aliases

SELECT last_name "Name" , salary*12 "Annual Salary"

FROM employees;

SELECT last_name AS name, commission_pct comm

FROM employees;


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Concatenation Operator

A concatenation operator:

Links columns or character strings to othercolumns

Is represented by two vertical bars (||) Creates a resultant column that is a character

expression

SELECT last_name||job_id AS "Employees"

FROM employees;


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Literal Character Strings

A literal is a character, a number, or a datethat is included in the SELECT statement.

Date and character literal values must beenclosed by single quotation marks.

Each character string is output once foreachrow returned.


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Using Literal Character Strings

SELECT last_name ||' is a '||job_id

AS "Employee Details"

FROM employees;


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Alternative Quote (q)

Operator Specify your own quotation mark delimiter

Choose any delimiter

Increase readability and usability

SELECT department_name ||q'[, it's assigned Manager Id: ]'

|| manager_id

AS "Department and Manager"

FROM departments;


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Duplicate Rows

The default display of queries is all rows, includingduplicate rows.

SELECT department_id

FROM employees;

SELECT DISTINCT department_id

FROM employees;

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2


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Summary

In this lesson, you should havelearned 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 moredescriptive column headings

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

FROMtable;


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Practice 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;


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Practice 1 :

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

5-The HR department has requested a report of all

employees and their job IDs. Display the lastname concatenated with the job ID (separated

by a comma and space) and name the column

Employee and Title.


23/45Copyright 2004, Oracle. All rights reserved.

2-Restricting and Sorting Data

ORACLE


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Objectives

After completing this lesson, you

should be able to do the following:

Limit the rows that are retrieved by aquery

Sort the rows that are retrieved by a

query


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Limiting Rows Using a

Selection

retrieve all

employees indepartment 90

EMPLOYEES


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Limiting the Rows That Are

Selected

Restrict the rows that are returned by using theWHERE clause:

The WHERE clause follows the FROM clause.

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

FROM table

[WHERE condition(s)];


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SELECT employee_id, last_name, job_id, department_id

FROM employees

WHERE department_id = 90 ;

Using the WHERE Clause


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SELECT last_name, job_id, department_id

FROM employees

WHERE last_name = 'Whalen' ;

Character Strings and Dates

Character strings and date values areenclosed by single quotation marks.

Character values are case-sensitive, and

date values are format-sensitive. The default date format is DD-MON-RR.


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Comparison Conditions

Operator Meaning

= Equal to

> Greater than

>= Greater than or equal to< Less than


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SELECT last_name, salary

FROM employees

WHERE salary


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SELECT last_name, salaryFROM employees

WHERE salary BETWEEN 2500 AND 3500 ;

Using the BETWEEN Condition

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

Lower limit Upper limit


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SELECT employee_id, last_name, salary, manager_id

FROM employees

WHERE manager_id IN (100, 101, 201) ;

Using the IN Condition

Use the IN membership condition to test for values ina list:


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SELECT first_name

FROM employeesWHERE first_name LIKE 'S%' ;

Using the LIKE Condition

Use the LIKE condition to perform wildcardsearches of valid search string values.

Search conditions can contain either literalcharacters or numbers: % denotes zero or many characters.

_ denotes one character.


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Using the LIKE Condition

You can combine pattern-matchingcharacters:

SELECT last_name

FROM employees

WHERE last_name LIKE '_o%' ;


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SELECT last_name, manager_id

FROM employees

WHERE manager_id IS NULL ;

Using the NULL Conditions

Test for nulls with the IS NULL operator.


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Logical Conditions

Operator Meaning

AND Returns TRUE ifbothcomponent

conditions are true

OR Returns TRUE ifeithercomponent

condition is true

NOT Returns TRUE if the following

condition is false


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SELECT employee_id, last_name, job_id, salary

FROM employees

WHERE salary >=10000

AND job_id LIKE '%MAN%' ;

Using the AND Operator

AND requires both conditions to be true:


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SELECT employee_id, last_name, job_id, salaryFROM employees

WHERE salary >= 10000

OR job_id LIKE '%MAN%' ;

Using the OR Operator

OR requires either condition to be true:


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SELECT last_name, job_id

FROM employees

WHERE job_id

NOT IN ('IT_PROG', 'ST_CLERK', 'SA_REP') ;

Using the NOT Operator


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Rules of Precedence

You can use parentheses to override rules ofprecedence.

Operator Meaning

1 Arithmetic operators

2 Concatenation operator

3 Comparison conditions

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

5 [NOT] BETWEEN

6 Not equal to

7 NOT logical condition

8 AND logical condition

9 ORlogical condition


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SELECT last_name, job_id, salaryFROM employees

WHERE job_id = 'SA_REP'

OR job_id = 'AD_PRES'

AND salary > 15000;

Rules of Precedence

SELECT last_name, job_id, salary

FROM employees

WHERE (job_id = 'SA_REP'OR job_id = 'AD_PRES')

AND salary > 15000;

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2


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Using the ORDER BY Clause

Sort retrieved rows with the ORDER BYclause: ASC: ascending order, default

DESC: descending order

The ORDER BY clause comes last in theSELECT statement:SELECT last_name, job_id, department_id, hire_date

FROM employees

ORDER BY hire_date ;


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Sorting

Sorting in descending order:

Sorting by column alias:

Sorting by multiple columns:

SELECT last_name, job_id, department_id, hire_date

FROM employees

ORDER BY hire_date DESC ; 1

SELECT employee_id, last_name, salary*12 annsal

FROM employees

ORDER BY annsal ;2

SELECT last_name, department_id, salary

FROM employees

ORDER BY department_id, salary DESC;

3


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

[WHERE condition(s)]

[ORDER BY {column, expr, alias} [ASC|DESC]] ;

Summary

In this lesson, you should have learned howto: 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 ofoutput


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Practice 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 ofall 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 jobis SA_REP orST_CLERKand whose salary is not equal to

$2,500, $3,500, or $7,000.

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