从多个不相关的表中获取数据

Question

考虑这两个表：

Product1
----------
id
created

Product2
---------
id
created

如何通过Product1订购Product2和created的所有产品？

注意：Product1和Product2表只是解释我案例的例子，它们并不反映现实。请不要就此进行辩论。

Answer 1

<强> You can Combining Result Sets by Using MySQL UNION

SQLFiddle

SELECT * FROM (select p1.id, p1.created from product1 p1
UNION ALL
select p2.id, p2.created from product2 p2) A 
order by created

或

(select p1.id, p1.created from product1 p1)
UNION ALL (select p2.id, p2.created from product2 p2)
ORDER BY created

Answer 2

假设两个表具有相同的结构，您可以尝试这个

SELECT
    'Product1' AS FromTable
    ,id
    ,created
FROM
    Product1
UNION
SELECT
    'Product2' AS FromTable
    ,id
    ,created
FROM
    Product2
ORDER BY created

Answer 3

使用交叉连接（也称为笛卡尔连接）

select product1.*, product2.* from product1 cross join product2;

请注意，交叉连接会使记录倍增。以下是mysql cross join, but without duplicated pair?

的答案