Select * from t1 Where (t1.c2=100) and Case When @Par1=1 then (t1.c1<0) When @Par1=2 then (t1.c1>0) When @Par1=3 then (t1.c1=0)
Select * from t1 Where (t1.c2=100) and Case When @Par1=1 and (t1.c1<0) then 1 When @Par1=2 and (t1.c1>0) then 1 When @Par1=3 and (t1.c1=0) then 1 ELSE 0 END=1