POS is the preferred built-in function for obtaining the position of one string in another. See page POS (Position) for a complete description.
returns the character position of one string, needle, in another, haystack, or returns 0 if the string needle is not found or is a null string. By default the search starts at the first character of haystack (start has the value 1). You can override this by specifying a different start point, which must be a positive whole number.
INDEX('abcdef','cd') -> 3
INDEX('abcdef','xd') -> 0
INDEX('abcdef','bc',3) -> 0
INDEX('abcabc','bc',3) -> 5
INDEX('abcabc','bc',6) -> 0