ÿþselect * FROM (select 1 id ,1 a,2 b,3 c

   union 

select 2 id ,2 a,3 b ,4 c

   union

select 3 id ,2 a,4 b, 5 c

   union

select 4 id ,3 a,6 b, 5 c

   union

select 5 id ,4 a,4 b, 3 c

   union

select 6 id ,5 a,3 b, 5 c

) t

   

WHERE

   CASE 3 WHEN 1 THEN -- ONLY 1,2,3

      A=1 AND B=2 AND c=3 --1 row

   WHEN 2 THEN --No1,2,3

      CASE 4 WHEN 4 THEN

         A=2 -- 2 rows

      WHEN 5 THEN

         C=3 -- 2 rows

      WHEN 6 THEN

         A=2 OR C=3 --4 rows

      END

   WHEN 3 THEN --Both 123 and No123

      ( A=1 AND B=2 AND c=3) OR

      CASE 9 WHEN 7 THEN

        ( A=2)  -- 3 rows

      WHEN 8 THEN

         ( C=3) --3 ROW

      WHEN 9 THEN

         (A=2 OR C=3) --4 ROW

      END

   END