You can use local variables in a counter in a while loop, for performing matching in a where clause and in an if statement, and for setting and resetting values in select statements.
/* Determine if a given au_id has a row in au_pix*/ /* Turn off result counting */ set nocount on /* declare the variables */ declare @c int, @min_id varchar(30) /*First, count the rows*/ select @c = count(*) from authors /* Initialize @min_id to "" */ select @min_id = "" /* while loop executes once for each authors row */ while @c > 0 begin /*Find the smallest au_id*/ select @min_id = min(au_id) from authors where au_id > @min_id /*Is there a match in au_pix?*/ if exists (select au_id from au_pix where au_id = @min_id) begin print "A Match! %1!", @min_id end select @c = @c -1 /*decrement the counter */ end