LOCATE

Syntax:
LOCATE(substr,str), LOCATE(substr,str,pos)

The first syntax returns the position of the first occurrence of
substring substr in string str. The second syntax returns the position
of the first occurrence of substring substr in string str, starting at
position pos. Returns 0 if substr is not in str. Returns NULL if any
argument is NULL.

URL: https://dev.mysql.com/doc/refman/8.0/en/string-functions.html