The subquery contains nonexistent columns--not bug!.

1. Phenomena

CREATE Table A as (select 1 as col_a), create table B as (select 2 as Col_b) SELECT * from a Where col_a in (select Col_a fro M b)

Where Col_a exists only in table_a, Table_b does not have the field, and the result of the entire statement can be executed successfully!

2. Reason:

The problem is confusing, and the reason for this is that "automatically looks for the outer layer when the column name in the subquery does not exist."

In other words, the above query is actually interpreted as a

SELECT * from a where col_a in (col_a)

The equivalent of the constraint that automatically shields the subquery.

3. Modification:

To prevent this from happening, you need to ensure that SQL in the subquery runs correctly, and then view the SQL as a whole

The subquery contains nonexistent columns--not bug!.