I have a relatively simple query.

SELECT DISTINCT
    tA.id   AS 'id'
    //as pointed out, I could just select tB.value without the case here
    ,CASE   WHEN  tB.udf_id IN ('1')
            THEN  tB.value
     END    AS 'side'
FROM tableA tA
INNER JOIN tableB   tB  ON  tA.id    = tB.id
WHERE tB.udf_id IN ('1')

tableA
|id| date     |
|--|----------|
|1 | 1/1/2023 |
|2 | 1/2/2023 |
|3 | 1/3/2023 |

tableB
|id|udf_id| value   |
|--|------|---------|
|1 | 1    | right   |
|1 | 2    | active  |
|2 | 1    | left    |
|2 | 2    | NULL    |
|3 | 3    | right   |
|3 | 3    | pending |

This will give me 1 row per "id" because of the WHERE clause.

Result Output
|id| value   |
|--|---------|
|1 | right   |
|2 | left    |
|3 | right   |

However, I now want to add another condition to what data gets returned. I only want to return results;

tB.value is not NULL when tB.udf_id=2
(pseudocode, I know this doesn't work this way)

So the new result output would look the same but drop id=2 because tb.value=NULLwhen tb.udf_id=2.

New Result Output
|id| value   |
|--|---------|
|1 | right   |
|3 | right   |

I'm struggling on how to do this. Just adding another udf_id value creates multiple rows of results instead of the one, which I don't want. And I don't believe I can express my codition in the WHERE clause like that.

My assumption is that I need to do some sort of subquery?