mysql>mysql> delimiter $$mysql>mysql> create function myfunction-> (in_string varchar(255),-> in_find_str varchar(20),-> in_repl_str varchar(20))->-> returns varchar(255)-> begin-> declare l_new_string varchar(255);-> declare l_find_pos int;->-> set l_find_pos=instr(in_string,in_find_str);->-> if (l_find_pos>0) then-> set l_new_string=insert(in_string,l_find_pos,length(in_find_str),in_repl_str);-> else-> set l_new_string=in_string;-> end if;-> return(l_new_string);->-> end$$query ok, 0 rows affected (0.00 sec)mysql>mysql> delimiter ;mysql> select myfunction('abc','a','z');+---------------------------+| myfunction('abc','a','z') |+---------------------------+| zbc |+---------------------------+1 row in set (0.00 sec)mysql> drop function myfunction;query ok, 0 rows affected (0.00 sec)