SQL WHERE Clause:

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

SQL WHERE Syntax

SELECT column_name(s) FROM table_name  WHERE column_name operator value

WHERE Clause Example

“Persons” TABLE:

P_Id	LastName	FirstName	Address	City
1	Suhail	Osmani	Maharaj Nagar	Sitapur
2	Maxwel	Tom	Biswan	Sitapur
3	Rahi	Ayon	Okhla	Delhi

Now we want to select only the persons living in the city "Sitapur" from the table above.
We use the following SELECT statement:

SELECT * FROM Persons WHERE City='Sitapur'

Output
:

P_Id	LastName	FirstName	Address	City
1	Suhail	Osmani	Maharaj Nagar	Sitapur
2	Maxwel	Tom	Biswan	Sitapur

6.Quotes Around Text Fields

Note:SQL uses single quotes around text values (most database systems will also accept double quotes).
Although, numeric values should not be enclosed in quotes.


For text values:

This is correct: SELECT * FROM Persons WHERE FirstName='Tom' This is wrong: SELECT * FROM Persons WHERE FirstName=Tom

For numeric values:

This is correct: SELECT * FROM Persons WHERE Year=1965 This is wrong: SELECT * FROM Persons WHERE Year='1965'

Operators Allowed in the WHERE Clause

With the WHERE clause, the following operators can be used:      

                                      

Operator	Description
=	Equal
<>	Not equal
>	Greater than
<	Less than
>=	Greater than or equal
<=	Less than or equal
BETWEEN	Between an inclusive range
LIKE	Search for a pattern
IN	If you know the exact value you want to return for at least one of the columns

Note: In some versions of SQL the <> operator may be written as !=