Alibabacloud, Database, Query Optimization, Sql, Relational Databases.
query, the prerequisite is that t1.c3 is less than 0. In this case, the correlation conditions where the subquery is involved in should have no filter degree, while some rows are filtered after rewriting as inner join. It is not semantically equivalent. Select t1.c2 From t1 Where t1.c3 < ( Select