Empty scalar subquery
Applies to ✅ Open Source Edition ✅ Express Edition ✅ Professional Edition ✅ Enterprise Edition
When a scalar subquery is provably empty, we can replace it with NULL.
Using Settings.transformPatternsEmptyScalarSubquery, the following transformations can be achieved:
-- With Settings.transformPatternsEmptyScalarSubquery active, this: SELECT (SELECT c FROM tab WHERE FALSE); -- ... is transformed into the equivalent expression: SELECT NULL -- (SELECT c FROM tab WHERE FALSE);
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