SQL WHERE Clause

The WHERE clause is used to filter records.

The WHERE Clause

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

SELECT column_name(s)
FROM table_name
WHERE column_name operator value

The "Persons" table:

P_Id	LastName	FirstName	Address	City
1	Karmen	Kasa	Los Angels - USA	New Orleans
2	Jacob	Mary	Los Angels - USA	New Orleans
3	Maxwell	Glen	Australia	Sydney

Now we want to select only the persons living in the city "New Orleans" from the table above.

We use the following SELECT statement:

SELECT * FROM Persons
WHERE City='New Orleans'

The result-set will look like this:

P_Id	LastName	FirstName	Address	City
1	Karmen	Kasa	Los Angels - USA	New Orleans
2	Jacob	Mary	Los Angels - USA	New Orleans

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='Mary'

This is wrong:

SELECT * FROM Persons WHERE FirstName=Mary

For numeric values:

This is correct:

SELECT * FROM Persons WHERE Year=1965

This is wrong:

SELECT * FROM Persons WHERE Year='1965'

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 !=