WHERE Clause

This Oracle tutorial explains how to use the Oracle WHERE clause with syntax and examples.

Description

The Oracle WHERE clause is used to filter the results from a SELECT, INSERT, UPDATE, or DELETE statement.

Syntax

The syntax for the WHERE clause in Oracle/PLSQL is:

WHERE conditions;

Parameters or Arguments

conditions

The conditions that must be met for records to be selected.

Example - With Single condition

It is difficult to explain the syntax for the Oracle WHERE clause, so let's look at some examples.

SELECT *

FROM customers

WHERE last_name = 'Anderson';

In this Oracle WHERE clause example, we've used the WHERE clause to filter our results from the customers table. The SELECT statement above would return all rows from the customers table where the last_name is Anderson. Because the * is used in the SELECT, all fields from the customers table would appear in the result set.

Example - Using AND condition

SELECT *

FROM suppliers

WHERE state = 'California'

AND supplier_id <= 750;

This Oracle WHERE clause example uses the WHERE clause to define multiple conditions. In this case, this SELECT statement uses the AND condition to return all suppliers that are located in the state of California and whose supplier_id is less than or equal to 750.

Example - Using OR condition

SELECT supplier_id

FROM suppliers

WHERE supplier_name = 'Apple'

OR supplier_name = 'Microsoft';

This Oracle WHERE clause example uses the WHERE clause to define multiple conditions, but instead of using the AND condition, it uses the OR condition. In this case, this SELECT statement would return all supplier_id values where the supplier_name is Apple or Microsoft.

Example - Combining AND & OR conditions

SELECT *

FROM suppliers

WHERE (state = 'Florida' AND supplier_name = 'IBM')

OR (supplier_id > 5000);

This Oracle WHERE clause example uses the WHERE clause to define multiple conditions, but it combines the AND condition and the OR condition. This example would return all suppliers that reside in the state of Florida and whose supplier_name is IBM as well as all suppliers whose supplier_id is greater than 5000.

The parentheses determine the order that the AND and OR conditions are evaluated. Just like you learned in the order of operations in Math class!

Example - Joining Tables

SELECT suppliers.suppler_name, orders.order_id

FROM suppliers

INNER JOIN orders

ON suppliers.supplier_id = orders.supplier_id

WHERE suppliers.state = 'California';

This Oracle WHERE clause example uses the WHERE clause to join multiple tables together in a single SELECT statement. This SELECT statement would return all supplier_name and order_id values where there is a matching record in the suppliers and orders tables based on supplier_id, and where the supplier's state is California.