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.
WHERE 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 in the Northwind sample database:
| 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 |
WHERE Clause Example
The following SQL statement selects all the customers from the country "Mexico", in the "Customers" table:
Example
SELECT * FROM Customers
WHERE Country='Mexico';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
The following operators can be used in the WHERE clause:
|
SR.NO |
Operator |
Description Example |
|
1 |
= |
Equal |
|
2 |
> |
Greater than |
|
3 |
< |
Less than |
|
4 |
>= |
Greater than or equal |
|
5 |
<= |
Less than or equal |
|
6 |
<> |
Not equal. Note: In some versions of SQL this operator may be written as != |
|
7 |
BETWEEN |
Between a certain range |
|
8 |
LIKE |
Search for a pattern |
|
9 |
IN |
To specify multiple possible values for a column |