Question

如果我不做UNION，我有这个查询正常工作：

SELECT t1.offer_id, t1.cpv_id, t1.type,
FROM `offer_cpv` t1
JOIN `offer` t2     ON t1.offer_id = t2.id
JOIN `company` t3   ON t2.cmpid = t3.id
WHERE t1.cpv_id = :cpvid
AND t3.status IN (4, 6)
GROUP BY t1.offer_id
ORDER BY t1.type

关键部分是我正在做ORDER BY t1.type。但是，如果我使用UNION（我必须），我的查询会断言：

'order clause'中的未知列't1.type'

以下是我的UNION尝试不起作用：

SELECT t1.offer_id, t1.cpv_id, t1.type,
FROM `offer_cpv` t1
JOIN `offer` t2    ON t1.offer_id = t2.id
JOIN `company` t3  ON t2.cmpid = t3.id
WHERE t1.cpv_id = :cpvid
AND t3.status IN (4, 6)
GROUP BY t1.offer_id
ORDER BY t1.type

UNION

SELECT t1.offer_id, t1.cpv_id, t1.type,
FROM `offer_cpv` t1
JOIN `offer` t2      ON t1.offer_id = t2.id
JOIN `company_2` t3  ON t2.cmpid = t3.id
WHERE t1.cpv_id = :cpvid
AND t3.status IN (4, 6)
GROUP BY t1.offer_id

ORDER BY t1.type

和

SELECT t1.offer_id, t1.cpv_id, t1.type,
FROM `offer_cpv` t1
JOIN `offer` t2    ON t1.offer_id = t2.id
JOIN `company` t3  ON t2.cmpid = t3.id
WHERE t1.cpv_id = :cpvid
AND t3.status IN (4, 6)
GROUP BY t1.offer_id

UNION

SELECT t1.offer_id, t1.cpv_id, t1.type,
FROM `offer_cpv` t1
JOIN `offer` t2      ON t1.offer_id = t2.id
JOIN `company_2` t3  ON t2.cmpid = t3.id
WHERE t1.cpv_id = :cpvid
AND t3.status IN (4, 6)
GROUP BY t1.offer_id

ORDER BY t1.type

我可以以某种方式执行此UNION，但按类型排序结果。我按类型排序，因为我需要得到这样的输出：

<h2> Results of type 1 from both tables: </h2>
<div> Result 1 from **first** table </div>
<div> Result 2 from first table </div>
<div> Result 1 from **second** table </div>
<div> Result 2 from second table </div>
<h2> Results of type 2 from both tables: </h2>
<div> Result 1 from **first** table </div>
<div> Result 2 from first table </div>
<div> Result 1 from **second** table </div>
<div> Result 2 from second table </div>

稍后我将在ORDER BY子句中添加一个列：t1.rank，所以我可以先按类型排序，然后按排名排序！

Answer 1

您只能在整个UNION上订购。将t1.type的第一个ORDER BY别名删除为其他内容，例如＆＃34; mytype＆＃34;。然后将第二个ORDER BY更改为ORDER BY mytype。

见这里：

SQL Query - Using Order By in UNION

Answer 2

来自MySQL manual：

这种ORDER BY不能使用包含a的列引用表名（即tbl_name.col_name格式的名称）。代替，在第一个SELECT语句中提供列别名并引用 ORDER BY中的别名。（或者，请参阅中的列 ORDER BY使用其列位置。但是，使用列位置不推荐使用。）

所以基本上你需要（i）为你需要在第一个查询中排序的列创建别名（ii）使用ORDER BY子句中的别名：

SELECT t1.offer_id, t1.cpv_id, t1.type AS type_column --, t1.rank as rank_column
FROM `offer_cpv` t1
JOIN `offer` t2 ON t1.offer_id = t2.id
JOIN `company` t3 ON t2.cmpid = t3.id
WHERE t1.cpv_id = :cpvid AND t3.status IN (4, 6)
GROUP BY t1.offer_id

UNION

SELECT t1.offer_id, t1.cpv_id, t1.type --, t1.rank
FROM `offer_cpv` t1
JOIN `offer` t2 ON t1.offer_id = t2.id
JOIN `company_2` t3 ON t2.cmpid = t3.id
WHERE t1.cpv_id = :cpvid AND t3.status IN (4, 6)
GROUP BY t1.offer_id

ORDER BY type_column --, rank_column

在mysql中使用UNION时无法排序

2 个答案: