SQL Where
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
SQL
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.!
WHERE Clause Example
The following SQL statement selects all the customers from the country “Mexico”, in the “Customers” table:
SQL
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:
SQL
SELECT * FROM Customers
WHERE CustomerID=1;
Operators in The WHERE Clause
The following operators can be used in the WHERE
clause:
Operator | Description |
---|---|
= | 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 |
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