The STUFF function inserts a string into another string. It deletes a specified length of characters in the first string at the start position and then inserts the second string into the first string at the start position.
charexpression
Is an expression of character data. character_expression can be a constant, variable, or column of either character or binary data.
start
Is an integer value that specifies the location to start deletion and insertion. If start or length is negative, a null string is returned. If start is longer than the first charexpression, a null string is returned.
length
Is an integer that specifies the number of characters to delete. If length is longer than the first charexpression, deletion occurs up to the last character in the last charexpression.