SQL WHERE

The SQL WHERE Clause

The WHERE clause serves to extract records that meet specific conditions, filtering out those that do not satisfy the specified criteria.

Example

Retrieve all customers who are located in Mexico.

SELECT * FROM Customers
WHERE Country=‘Mexico’;

Syntax

SELECT column1, column2, ...

FROM table_name

WHERE condition;

Note: The WHERE clause is employed not only in SELECT statements but also in UPDATE, DELETE, and other SQL operations.

Demo Database

Here is a segment from the Customers table utilized 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

In SQL, text values must be enclosed in single quotes (double quotes may also be accepted by most database systems), while numeric fields should not be enclosed in quotes.

Example

SELECT * FROM Customers
WHERE CustomerID=1;

Operators in The WHERE Clause

Alternative operators beyond “=” can be utilized to refine search filters.

Example

Retrieve all customers whose CustomerID exceeds 80.

SELECT * FROM Customers
WHERE CustomerID > 80;

Various operators are available for use within the WHERE clause:

Operator	Description
=	Equal
>	Greater than
<	Less than
>=	Greater than or equal
<=	Less than or equal
<>	Not equivalent. Note: In certain SQL versions, this operator might be expressed as !=
BETWEEN	Within a specific range.
LIKE	Please find a pattern.
IN	To delineate multiple potential values for a column.