Question: In a WHERE part of query we have

```
SELECT * FROM SomeTable st
WHERE 
NOT EXISTS 
  (SELECT 1 FROM Tab t1 WHERE t1.A = st.A OR t1.B = st.A)
OR EXISTS 
  (SELECT 1 FROM Tab t2 WHERE (t2.A = st.A OR t2.B = st.A) AND t2.C IS NULL)

```

Seems like a good candidate for merging...
But I'm staring on that for an hour without any idea.

Would you have some thoughts?

Thanks,

Answer: 
```
SELECT distinct st.* 
FROM SomeTable st 
     left outer join Tab t
     on st.a in (t.a,t.b)
WHERE t.c is null

```

Sometimes the simplest answer is to use a join rather than an exists.
Try:

```
NOT EXISTS (SELECT 1 FROM Tab WHERE (Tab.A = @Id OR Tab.B = @ID)
            AND (Tab.C is null OR Tab.C != @Var))

```