MySQL ALL 子句中的多列

Question

为什么不允许执行以下操作？

SELECT Column_1
FROM Mytable
WHERE (Column_1, Column_2) >= ALL(SELECT Column_1,Column_2 FROM MYTABLE2)

但是可以做到

SELECT Column_1
FROM Mytable
WHERE (Column_1, Column_2) IN (SELECT Column_1,Column_2 FROM MYTABLE2)

Answer 1

假设这是您要编写的查询：

select col1 from t1 where (col1, col2) > all(select col1, col2 from t2);

这在 MySQL 中不起作用，并引发错误：

Operand should contain 1 column(s)

MySQL 虽然支持元组（不）相等，所以你可以用 not exists:

来表达

select col1 
from t1
where not exists (
    select 1
    from t2
    where (t2.col1, t2.col2) > (t1.col1, t1.col2)
)

MySQL multiple columns in ALL clause