FIND_IN_SET() function, as name specified, is used to search the specified string from the list of string. Basically it returns the position of a string, if it is present (as a substring), within a list of strings.
Syntax
FIND_IN_SET(Search String, string list)
Here, search string is the string which is to be searched and string list is the string that contains the substrings separated by commas.
Example
mysql> Select FIND_IN_SET('good','Ram,is,a,good,boy');
+-----------------------------------------+
| FIND_IN_SET('good','Ram,is,a,good,boy') |
+-----------------------------------------+
| 4 |
+-----------------------------------------+
1 row in set (0.00 sec)