SQL WHERE Clause

The SQL WHERE Clause

The WHERE clause is used to filter records.

It is used to extract only those records that fulfill a specified condition.

Example

Select all customers from Mexico:

SELECT * FROM Customers
WHERE Country='Mexico';

Syntax

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

Note: The WHERE clause is not only used in
SELECT statements, it is also used in UPDATE, DELETE, etc.!

Demo Database

Below is a selection from the Customers table used in the examples:

CustomerID CustomerName ContactName Address City PostalCode Country
1 Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany
2 Ana Trujillo Emparedados y helados Ana Trujillo Avda. de la Constitución 2222 México D.F. 05021 Mexico
3 Antonio Moreno Taquería Antonio Moreno Mataderos 2312 México D.F. 05023 Mexico
4 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbköp Christina Berglund Berguvsvägen 8 Luleå S-958 22 Sweden

Text Fields vs. Numeric Fields

SQL requires single quotes around text values (most database systems will also allow double quotes).

However, numeric fields should not be enclosed in quotes:

Example

SELECT * FROM Customers
WHERE CustomerID=1;

Operators in The WHERE Clause

You can use other operators than the = operator to filter the search.

Example

Select all customers with a CustomerID greater than 80 :

SELECT * FROM Customers
WHERE CustomerID > 80;

The following operators can be used in the WHERE clause:

Operator Description Example
= Equal

 

 

> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
<> Not equal. Note: In some versions of SQL this operator may be written as !=
BETWEEN Between a certain range
LIKE Search for a pattern
IN To specify multiple possible values for a column