SQL- Introduction to MySQL

Introduction toIntroduction to
MySQLMySQL

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

BasicBasic SELECTSELECT StatementStatement
◦ 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 SpecificSelecting Specific
ColumnsColumns
SELECT department_id, location_id
FROM 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.
Operator Description
+ Add
- Subtract
* Multiply
/ Divide

SELECT last_name, salary, salary + 300
FROM employees;
Using ArithmeticUsing Arithmetic
OperatorsOperators
…

SELECT last_name, salary, 12*salary+100
FROM employees;
Operator PrecedenceOperator Precedence
SELECT last_name, salary, 12*(salary+100)
FROM employees;
…
…
1
2

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

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 each
row returned.

Using Literal CharacterUsing Literal Character
StringsStrings
…
SELECT last_name ||' is a '||job_id
AS "Employee Details"
FROM employees;

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
FROM table;

Practice 1: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;

Practice 1 :Practice 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.

Limiting Rows Using aLimiting Rows Using a
SelectionSelection
“retrieve all
employees in
department 90”
EMPLOYEES
…

Limiting the Rows ThatLimiting the Rows That
Are SelectedAre Selected
◦ 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_id
FROM employees
WHERE department_id = 90 ;
Using theUsing the WHEREWHERE ClauseClause

SELECT last_name, job_id, department_id
FROM employees
WHERE last_name = 'Whalen' ;
Character Strings andCharacter 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
Operator Meaning
= 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
LIKE Match a character pattern
IS NULL Is a null value

SELECT last_name, salary
FROM employees
WHERE salary <= 3000 ;
Using ComparisonUsing Comparison
ConditionsConditions

SELECT last_name, salary
FROM employees
WHERE salary BETWEEN 2500 AND 3500 ;
Using theUsing 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_id
FROM employees
WHERE manager_id IN (100, 101, 201) ;
Using theUsing the ININ ConditionCondition
Use the IN membership condition to test for
values in a list:

SELECT first_name
FROM employees
WHERE first_name LIKE 'S%' ;
Using theUsing the LIKELIKE ConditionCondition
◦ 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 theUsing the LIKELIKE ConditionCondition
◦ You can combine pattern-matching characters:
SELECT last_name
FROM employees
WHERE last_name LIKE '_o%' ;

SELECT last_name, manager_id
FROM employees
WHERE manager_id IS NULL ;
Using theUsing the NULLNULL
ConditionsConditions
Test for nulls with the IS NULL operator.

Logical ConditionsLogical Conditions
Operator Meaning
AND Returns TRUE if both component
conditions are true
OR Returns TRUE if either component
condition is true
NOT Returns TRUE if the following
condition is false

SELECT employee_id, last_name, job_id, salary
FROM employees
WHERE salary >=10000
AND job_id LIKE '%MAN%' ;
Using theUsing the ANDAND OperatorOperator
AND requires both conditions to be true:

SELECT employee_id, last_name, job_id, salary
FROM employees
WHERE salary >= 10000
OR job_id LIKE '%MAN%' ;
Using theUsing the OROR OperatorOperator
OR requires either condition to be true:

SELECT last_name, job_id
FROM employees
WHERE job_id
NOT IN ('IT_PROG', 'ST_CLERK', 'SA_REP') ;
Using theUsing the NOTNOT OperatorOperator

Rules of PrecedenceRules of Precedence
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 OR logical condition

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 2: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 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.

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SQL- Introduction to MySQL

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