SQL WHERE Clause

The WHERE clause is used to filter records.

SQL WHERE Clause

The WHERE clause is used to extract only those records that fulfill a specified condition.

SQL WHERE Syntax

SELECT column1, column2, ...
FROM table_name
WHERE condition;

Parameter Explanation:

• column1, column2, ...: The names of the fields to select. Multiple fields can be specified. If no field names are specified, all fields will be selected.

• table_name: The name of the table to query.

Demonstration Database

In this tutorial, we will use the tutorialpro sample database.

Below is the data from the "Websites" table:

+----+--------------+---------------------------+-------+---------+
| id | name         | url                       | alexa | country |
+----+--------------+---------------------------+-------+---------+
| 1  | Google       | https://www.google.cm/    | 1     | USA     |
| 2  | Taobao       | https://www.taobao.com/   | 13    | CN      |
| 3  | tutorialpro.org      | http://www.tutorialpro.org/    | 4689  | CN      |
| 4  | Weibo        | http://weibo.com/         | 20    | CN      |
| 5  | Facebook     | https://www.facebook.com/ | 3     | USA     |
+----+--------------+---------------------------+-------+---------+

WHERE Clause Example

The following SQL statement selects all websites from the "Websites" table where the country is "CN":

Example

SELECT * FROM Websites WHERE country='CN';

Execution Output:

Text Fields vs. Numeric Fields

SQL uses single quotes to enclose text values (most database systems also accept double quotes).

In the previous example, the text field 'CN' used single quotes.

For numeric fields, do not use quotes.

Example

SELECT * FROM Websites WHERE id=1;

Execution Output:

Operators in the WHERE Clause

The following operators can be used in the WHERE clause: