Question

当人们在我的网站上搜索时，我使用UNION查询从不同的表中引入结果。人员，地点和活动。

我想按字母顺序对“人物”，“场地”按字母排序，对事件“ 反向”按字母排序，因为它们以一年开始，所以我希望最近的事件排在最前。 >

这是我目前所拥有的（已大大简化，但您明白了）。除了我希望对事件进行反向排序之外，它运行得很好。

我可以通过这个UNION查询达到最终目的，还是需要将其分解为多个单独的查询？如果需要的话，我没有问题，但是由于代码可以正常工作，因此，如果有人可以想到一个巧妙的技巧，我希望对下面的查询做一个小的简单更改。

SELECT name AS name
     , name AS order
     , 1    AS grp

FROM PEOPLE

UNION

SELECT venue AS name
     , venue AS order
     , 2     AS grp

FROM VENUES

UNION

SELECT event AS name
     , event AS order
     , 3     AS grp

FROM EVENTS

ORDER BY grp ASC, order ASC

例如，如果我可以将event AS order更改为STRING_SUBTRACT('ZZZZZZ', event) AS order或类似的名称。我可以使用任何此类功能吗？

Answer 1

UNION只会在一个表之后追加另一个表。编写三个简单的查询，并在它们之间使用联合。在您的情况下，按条件应用三种不同的顺序，就像您在前面的示例中一样，对每个查询应用一种。

(SELECT name AS name
     , name AS order
     , 1    AS grp
FROM PEOPLE
ORDER BY name asc)

UNION

(SELECT venue AS name
     , venue AS order
     , 2     AS grp
FROM VENUES
ORDER BY venue ASC)

UNION

(SELECT event AS name
     , event AS order
     , 3     AS grp

FROM EVENTS
ORDER BY event DESC)

不同的故事，如果要订购统一的结果，将它们混合在表之间

Answer 2

这是我到目前为止提出的答案：

SELECT name AS name
     , name AS orderByAsc
     , ''   AS orderByDesc
     , 1    AS grp

FROM PEOPLE

UNION

SELECT venue AS name
     , venue AS orderByAsc
     , ''    AS orderByDesc
     , 2     AS grp

FROM VENUES

UNION

SELECT event AS name
     , ''    AS orderByAsc
     , event AS orderByDesc
     , 3     AS grp

FROM EVENTS

ORDER BY grp ASC
       , orderByDesc DESC
       , orderByAsc ASC

完美运行。

如何按不同条件对UNION MySQL查询的不同部分进行排序？

2 个答案: