I have this query

```
SELECT (SELECT cost FROM table1 t2 WHERE t2.edate=>table1.edate) AS cost
FROM table1
WHERE table1.orderNo = 'CS119484568'

```

the above query returns:

```
cost
4
3
null
null
5

```

I want to get sum of all or null if any row have a null

```
SELECT SUM((SELECT cost FROM table1 t2 WHERE t2.edate=>table1.edate)) AS cost
FROM table1
WHERE table1.orderNo = 'CS119484568'

```

Expected result NULL in the above case.