SQL Tutorial: 7

By alexxk5111

SQL WHERE – SQL Tutorial

The SQL WHERE clause is used to select data conditionally, by adding it to already existing SQL SELECT query. We are going to use the Customers table from the previous chapter, to illustrate the use of the SQL WHERE command.

Table: Customers

FirstNameLastNameEmailDOBPhone
JohnSmith[email protected]2/4/1968626 222-2222
StevenGoldfish[email protected]4/4/1974323 455-4545
PaulaBrown[email protected]5/24/1978416 323-3232
JamesSmith[email protected]20/10/1980416 323-8888

If we want to select all customers from our database table, having last name ‘Smith’ we need to use the following SQL syntax:


SELECT *
FROM Customers
WHERE LastName = ‘Smith’

The result of the SQL expression above will be the following:

FirstNameLastNameEmailDOBPhone
JohnSmith[email protected]2/4/1968626 222-2222
JamesSmith[email protected]20/10/1980416 323-8888

In this simple SQL query we used the “=” (Equal) operator in our WHERE criteria:

LastName = ‘Smith’

But we can use any of the following comparison operators in conjunction with the SQL WHERE clause:

<> (Not Equal)


SELECT *
FROM Customers
WHERE LastName <> ‘Smith’

> (Greater than)


SELECT *
FROM Customers
WHERE DOB > ‘1/1/1970’

>= (Greater or Equal)


SELECT *
FROM Customers
WHERE DOB >= ‘1/1/1970’

< (Less than)


SELECT *
FROM Customers
WHERE DOB < ‘1/1/1970’

<= (Less or Equal)


SELECT *
FROM Customers
WHERE DOB =< ‘1/1/1970’

LIKE (similar to)


SELECT *
FROM Customers
WHERE Phone LIKE ‘626%’

Note the LIKE syntax is different with the different RDBMS (SQL Server syntax used above).

Between (Defines a range)


SELECT *
FROM Customers
WHERE DOB BETWEEN ‘1/1/1970’ AND ‘1/1/1975’