INSTR searches string for substring.
--> position is an integer indicating the character of string where SQL Server begins the search.
-->If position is negative, SQL Server counts and searches backward from the end of string.
occurrence is an integer indicating which occurrence of string SQL Server should search for.
The value of occurrence must be positive. The function returns an integer indicating the position of the
character in string that is the first character of this occurrence. The default values of both position and
occurrence are 1, meaning SQL Server begins searching at the first character of string for the first occurrence
of substring. The return value is relative to the beginning of string, regardless of the value of position,
and is expressed in characters. If the search is unsuccessful (if substring does not appear occurrence times
after the position character of string) the return value is 0.