SQL Server Function

 STUFF :

The STUFF() function deletes a part of a string and then inserts another part into the string, starting at a specified position.

Note: Also look at the REPLACE() function.

Syntax:

STUFF(string, start, length, new_string)

Example: 

SELECT STUFF('SQL Tutorial!', 13, 1, ' is fun!');

CharIndex()

The CHARINDEX() function searches for a substring in a string, and returns the position.

If the substring is not found, this function returns 0.

Note: This function performs a case-insensitive search.

Syntax:

CHARINDEX(substring, string, start).

Example:

SELECT CHARINDEX('OM', 'Customer') AS MatchPosition