Oracle SQL Tutorials – Chapter 2 (Part 1 of 3)

CHAPTER 2

• WHERE Conditions
• Comparison operators
• BETWEEN operator
• IN operator
• LIKE operator
• IS NULL operator
• Logical operators
• AND operator
• OR operator
• NOT operator
• ORDER BY operator

RESTRICTING ROWS WITH WHERE

• WHERE statement can be used to return only specific rows.
• WHERE statement must be written after the SELECT statement.
• The condition that defined in the WHERE statement, can include; values in column , literal values, arithemtic expressions or functions.
• SELECT *|{[DISTINCT] column|expression [alias],…} FROM table [WHERE condition(s)

• Let’s list the employees which department_ID are 80.

SELECT employee_id, first_name,last_name, job_id, department_id 
FROM hr.employees
WHERE department_id=80;

COMPARISON OPERATORS

• Let’s list the employees which salary is 3000 or less.

SELECT first_name,last_name, salary 
FROM hr.employees 
WHERE salary <= 3000 ;

IN OPERATOR

• Let’s list the employees which Manager_id is 100, 101 or 201.

SELECT employee_id, first_name,last_name, salary, manager_id 
FROM hr.employees 
WHERE manager_id IN (100, 101, 201) ;

LIKE OPERATOR

• Let’s list the employees that has ‘e’ character in his/her name.

SELECT first_name,last_name 
FROM hr.employees 
WHERE first_name LIKE '%e%' ;

• Let’s list the employees that surname’s second character is ‘o’.

SELECT first_name,last_name
FROM hr.employees
WHERE last_name LIKE '_o%' ;

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Oracle SQL Tutorials – Chapter 2 (Part 2 of 3)