WHERE 谓词支持子查询，包括 IN 、 NOT IN 、 EXISTS 、 NOT EXISTS 和标量子查询。 不支持以下类型的子查询：

在大多数情况下，可以使用 NOT EXISTS 重写 NOT IN 子查询。 建议尽可能使用 NOT EXISTS ，因为执行带有 NOT IN 子查询的 DELETE 可能会速度较慢。

> DELETE FROM events WHERE date < '2017-01-01'
> DELETE FROM all_events
   WHERE session_time < (SELECT min(session_time) FROM good_events)
> DELETE FROM orders AS t1
   WHERE EXISTS (SELECT oid FROM returned_orders WHERE t1.oid = oid)
> DELETE FROM events
   WHERE category NOT IN (SELECT category FROM events2 WHERE date > '2001-01-01')
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