my $NULL = NULL;

set @query1 := (SELECT (field,) FROM table WHERE table='NULL' \G);
SELECT @query1 
set @query2 := (SELECT (field2) FROM table2 WHERE field2='NULL' \G);
SELECT @query2

IF (@query1) = $NULL { 
	set @query3 := (SELECT (field3) FROM table3 WHERE field3=(@query2) AND field4 LIKE 'test');

set query 5 := (UPDATE table5 SET field5=(@query3) WHERE field6=(@query2);