Tricky logical XOR for nullable values

Question

I have 2 nullable `CHAR` columns and I need to check if only one of them is null. Doing ``` (a IS NULL AND b IS NOT NULL) OR (a IS NOT NULL AND b IS NULL) ``` is boring. And I would like to avoid creating custom functions for that. I was thinking about something like ``` COALESCE(a, 1) + COALESCE(b, 1) = 1 ``` but as long as `a` is `char` - it causes operand type error. So, any tricky solutions?

Accepted Answer

If you mean exactly one is NULL (which matches your existing logic), then:

```
a is null != b is null
```

Tricky logical XOR for nullable values

Solution

Problem