Sql and Business Intelligence: SQL LIKE CLAUSE

We will use the Company table to illustrate the SQL LIKE clause usage:

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

The SQL LIKE clause is very useful when you want to specify a search condition within your SQL WHERE clause, based on a part of a column contents. For example if you want to select all Company having FirstName starting with 'J' you need to use the following SQL statement:

SELECT * FROM Company WHERE FirstName LIKE 'J%'

Here is the result of the SQL statement above:

FirstName	LastName	Email	DOB	Phone
Jackson	Jimmy	Jimmy@supermail.co.uk	20/10/1980	416 323-8888

If you want to select all Company with phone numbers starting with '416' you will use this SQL expression:

SELECT * FROM Company WHERE Phone LIKE '416%'.

The '%' is a so called wildcard character and represents any string in our pattern.You can put the wildcard anywhere in the string following the SQL LIKE clause and you can put as many wildcards as you like too.

Note that different databases use different characters as wildcard characters, for example '%' is a wildcard character for MS SQL Server representing any string, and '*' is the corresponding wildcard character used in MS Access.Another wildcard character is '_' representing any single character.

The '[]' specifies a range of characters. Have a look at the following SQL statement:

SELECT * FROM Company WHERE Phone LIKE '[4-6]_6%'.

This SQL expression will return all Company satisfying the following conditions:

* The Phone column starts with a digit between 4 and 6 ([4-6])

* Second character in the Phone column can be anything (_)

* The third character in the Phone column is 6 (6)

* The remainder of the Phone column can be any character string (%)

Here is the result of this SQL expression: