SQL WHERE Clause

The WHERE clause is used to filter records.

The SQL WHERE Clause

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

SELECT column_name,column_name
FROM table_name
WHERE column_name operator value;

In this tutorial we will use the well-known Northwind sample database.

Below is a selection from the "Customers" table:

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 Constitucion 2222	Mexico D.F.	05021	Mexico
3	Antonio Moreno Taqueria	Antonio Moreno	Mataderos 2312	Mexico D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbkop	Christina Berglund	Berguvsvagen 8	Lulea	S-958 22	Sweden

The following SQL statement selects all the customers from the country "Mexico", in the "Customers" table:

SELECT * FROM Customers
WHERE Country='Mexico';

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

However, numeric fields should not be enclosed in quotes:

SELECT * FROM Customers
WHERE CustomerID=1;

The following operators can be used in the WHERE clause:

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