MS SQL Server Interview Question:

What To Perform Pattern Match with the LIKE Operator?

Submitted by: Administrator

Pattern match is a very important operation for search records base on character string columns. SQL Server 2005 offers the LIKE operator to perform pattern match operations in two formats:

target_string LIKE pattern
-- Returns TRUE
if the target string matches the pattern

target_string NOT LIKE pattern
-- Returns TRUE
if the target string does not match the pattern

Pattern match is a powerful operation. But you need to remember several rules:

* Pattern may contain predefined wildcard characters, similar to Unix Regular Expressions. But they are not the same.
* '%' is a wildcard character that matches any string of zero or more characters.
* '_' is a wildcard character that matches any single character.
* '_' is a wildcard character that matches any single character.
* '[abc]' is a wildcard character that matches any character listed inside the brackets.
* '[a-c]' is a wildcard character that matches any character in the range defined in the brackets.
* '[^abc]' is a wildcard character that matches any character not listed inside the brackets.
* '[^a-c]' is a wildcard character that matches any character not in the range defined in the brackets.
Submitted by: Administrator

Here is a simple example of LIKE operator:

SELECT CASE WHEN
'GlobalGuideLine.com' LIKE 'Glo%'
THEN 'Pattern matched.'
ELSE 'Pattern not matched.'
END;
GO
Pattern matched.

Submitted by: Administrator