MySQL ORDER BY 第一个字段然后第二个字段

Question

这是我的实际查询：

    SELECT DISTINCT eventi.img AS img, posizione AS pos
    FROM eventi
    WHERE homepage =1
    UNION
    SELECT DISTINCT prodotti.img, prodotti.posizione
    FROM prodotti
    WHERE homepage =1 
    ORDER BY pos ASC

它 returns 像 "1,1,2,2" 这样的位置。我想要 returns 按字段定位，例如 "event position 1,2 -> then products position 1,2" 。现在它混合了事件和产品位置...

Answer 1

根据 docs，你有一个联合，你需要采取额外的步骤来确保联合的最终查询中的 order by 子句适用于所有查询，而不仅仅是最后的查询：

SELECT ...
UNION
SELECT ... ORDER     <--order final query only

v.s

(SELECT ...)
UNION
(SELECT ...) ORDER     <--order all queries as a single set

注意额外的 ().

Answer 2

你可以这样做：

SELECT t.img,t.pos FROM (
    SELECT DISTINCT 1 as order_col, eventi.img AS img, posizione AS pos
    FROM eventi
    WHERE homepage =1
    UNION
    SELECT DISTINCT 2 , prodotti.img, prodotti.posizione
    FROM prodotti
    WHERE homepage =1 ) t
ORDER BY t.order_col,t.pos

如果您不关心 selecting order_col 那么您可以避免使用 sub select 并在里面下订单。

MySQL ORDER BY 第一个字段然后第二个字段

MySQL ORDER BY first field then second field

mysql

sql-order-by