sql - Order By date 描述问题

Question

我有这些疑问：

(SELECT * FROM product WHERE var<>'0'ORDER BY date DESC)

和

(SELECT * FROM product WHERE var='0' ORDER BY date DESC).

当我尝试将两者的结果合二为一时

 (SELECT * FROM product WHERE var<>'0'ORDER BY date DESC) 
 UNION 
 (SELECT * FROM product WHERE var='0' ORDER BY date DESC)

结果失去了顺序...结果集首先包含所有var不为零的记录，然后是所有var为零的记录，但它们没有按日期排序...特别是顺序有效...为什么？我尝试使用唯一的顺序，但结果混合了 var 等于或不为零的记录...

score 5 · Accepted Answer

您必须最后申请订单：

SELECT * FROM product WHERE var<>'0'
UNION 
SELECT * FROM product WHERE var='0'
ORDER BY date DESC

如果您想保留两个部分的顺序，请编辑，所以首先使用var<>'0'（内部排序date DESC），然后全部使用var='0'（内部排序date DESC）：

SELECT * FROM product WHERE var<>'0'
UNION 
SELECT * FROM product WHERE var='0'
ORDER BY 
    CASE WHEN var<>'0' THEN 0 ELSE 1 END ASC,
    date DESC

score 2 · Accepted Answer

我相信您要做的是将结果集放在'0'最后，然后按日期对每个子集进行排序。在这种情况下，您可以忘记联合并改为执行以下操作：

SELECT *
FROM product
WHERE var IS NOT NULL
ORDER BY CASE WHEN var = '0' THEN 2 ELSE 1 END, date DESC

score 0 · Accepted Answer

SELECT * FROM product WHERE var<>'0'
UNION 
SELECT * FROM product WHERE var='0'
ORDER BY date DESC

相当于：

SELECT * FROM product
ORDER BY date DESC

3 回答 3