SELECT语句中的表达式

常规SELECT语句中的哪些地方允许使用表达式？后端无关紧要，我的意思是从概念（iso？）的角度来看更多。

例如，在进行一些基本测试时（使用 mysql8，但同样，我不关心特定的后端）似乎除了在LIMITorOFFSET地方之外的任何地方都允许它：

with tbl (num, str) as (
    select 1, 'a'
) 
SELECT
    (select num from tbl limit 1) select_expr -- select expression
FROM
    (select * from tbl limit 1) table_expr -- table expression
WHERE
    (select null from tbl)
    or 1 = (select num from tbl)
    or (select num from tbl) = (select num from tbl) -- filter expressions, can be lhs or rhs or single subselect
GROUP BY
    num, (select num from tbl) -- aggregate expression
HAVING
    (select num from tbl limit 1)
ORDER BY
    (select num from tbl limit 1)
LIMIT
    (select num from tbl limit 1) -- invalid
OFFSET
    (select num from tbl limit 1) -- invalid

回答