Incorrect results returned from UNION

[YuanchengJiang]

Describe the bug

In some cases with table joins, the UNION operator does not return the expected result.

To reproduce

Query 1: result = [(0,)]

(SELECT count(1) FROM telemetry as T1 JOIN telemetry as T2 ON T1.created=T2.created WHERE T1.event=0.0)

Query 2: result = [(4361,)] (could differ but not zero)

(SELECT count(1) FROM telemetry as T1 JOIN telemetry as T2 ON T1.event=T2.event)

Query 3 (i.e., Query 1 UNION Query 2): result = [(0,)] (buggy)

(SELECT count(1) FROM telemetry as T1 JOIN telemetry as T2 ON T1.created=T2.created WHERE T1.event=0.0) UNION (SELECT count(1) FROM telemetry as T1 JOIN telemetry as T2 ON T1.event=T2.event)

Expected Behavior

The expected result of Query 3 is [(0,4361)]

Environment

- **QuestDB version**: v7.3.1

Additional context

No response