如何在UNION MySQL查詢中使用ORDER BY和LIMIT

Question

我有一個小問題，我有一個這樣的MySQL查詢代碼：

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

如何在上面的查詢中添加ORDER BY a.id DESC LIMIT 0,10 ？ 謝謝你的幫助。

Answer 1

用另一個選擇包裝它。

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

除非您的意圖是對UNION之前的每個查詢進行ORDER BY和LIMIT否則只需添加

ORDER BY id DESC LIMIT 0,10

在查詢的底部。