SQL Where Command

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 Company table from the previous chapter, to illustrate the use of the SQL WHERE command.

Table: Company

FirstName	LastName	Email	DOB	Phone
Scott	Armstrong	Armstrong.yahoo.com	2/4/1968	887-676-2321
Adam	Red	red@himail.com	4/4/1978	792 343-2422
Santo	Harry	Harry@livingin.org	5/24/1978	416 323-3232
Jackson	Jimmy	Jimmy@supermail.co.uk	20/10/1980	416 323-8888

If we want to select all Company from our database table, having last name 'Armstrong' we need to use the following SQL syntax:

SELECT *
FROM Company
WHERE LastName = 'Armstrong'

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

FirstName	LastName	Email	DOB	Phone
Scott	Armstrong	Armstrong.yahoo.com	2/4/1968	887-676-2321

In this simple SQL query we used the "=" (Equal) operator in our WHERE criteria:
LastName = 'Armstrong'
 

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

<> (Not Equal)

SELECT *
FROM Company
WHERE LastName <> 'Armstrong'

> (Greater than)

SELECT *
FROM Company
WHERE DOB > '1/1/1970'

>= (Greater or Equal)

SELECT *
FROM Company
WHERE DOB >= '1/1/1970'

< (Less than)

SELECT *
FROM Company
WHERE DOB < '1/1/1970'

<= (Less or Equal)

SELECT *
FROM Company
WHERE DOB =< '1/1/1970'

LIKE (similar to)

SELECT *
FROM Company
WHERE Phone LIKE '626%'

Between (Defines a range)

SELECT *
FROM Company
WHERE DOB BETWEEN '1/1/1970' AND '1/1/1975'.

MORE BASIC SQL COMMANDS