mysql - 如何在 UNION mysql 查询中使用 ORDER BY 和 LIMIT

Question

我有一个小问题，我有一个这样的 MySQL 查询代码：

SELECT a.id, b.name AS itemName, b.slug AS itemSlug FROM table_idx a
INNER JOIN table_product b ON b.id = a.targetid AND a.target='PRODUCT'
WHERE a.memberid=$memberid
UNION
SELECT a.id, c.name AS itemName, c.slug AS itemSlug FROM table_idx a
INNER JOIN table_news c ON c.id = a.targetid AND a.target='NEWS'
WHERE a.memberid=$memberid
UNION
SELECT a.id, d.name AS itemName, d.slug AS itemSlug FROM table_idx a
INNER JOIN table_promo d ON d.id = a.targetid AND a.target='PROMO'
WHERE a.memberid=$memberid

如何ORDER BY a.id DESC LIMIT 0,10在上面的查询中添加？谢谢你的帮助。

Answer 1

用另一个选择包裹它。

SELECT * FROM (
SELECT a.id, b.name AS itemName, b.slug AS itemSlug FROM table_idx a
INNER JOIN table_product b ON b.id = a.targetid AND a.target='PRODUCT'
WHERE a.memberid=$memberid
UNION
SELECT a.id, c.name AS itemName, c.slug AS itemSlug FROM table_idx a
INNER JOIN table_news c ON c.id = a.targetid AND a.target='NEWS'
WHERE a.memberid=$memberid
UNION
SELECT a.id, d.name AS itemName, d.slug AS itemSlug FROM table_idx a
INNER JOIN table_promo d ON d.id = a.targetid AND a.target='PROMO'
WHERE a.memberid=$memberid
) AS t ORDER BY t.id DESC LIMIT 0,10

Answer 2

除非您的意图是ORDER BY和LIMIT之前的每个查询UNION，否则只需添加

ORDER BY id DESC LIMIT 0,10

在查询的底部。