The following code will produce lower case random string length 4
Code:
SET @number:=4;
set @string:='';
SET @sql:=REPLACE('SET @t:=BENCHMARK(X,@string:=concat(@string,char(FLOOR(97+ RAND()*26))));','X',@number);
prepare stm1 from @sql;
execute stm1 ;
select @string; OUTPUT