Question

我想知道，我们如何在基于Union的mysql_query中订购列表（DESC），当我们在PHP / MYSQL中获取此查询时，我们正在获取输出。但我们只是简单地将订单放在此查询中。

 (SELECT info.id 
 FROM info, 1_all 
 WHERE 1_all.id = info.id and 1_all.table_type = 'disp'  AND 1_all.year = '$year' AND  info.category IN (1,2,3) AND info.area IN (2,5,6)  
 GROUP BY resinfo.id ) 
UNION ALL 
 (SELECT info.id 
 FROM info, 2_all 
 WHERE 2_all.id = info.id and 2_all.table_type = 'disp' AND 2_all.year = '$year' AND info.category IN (1,2,3) AND info.area IN (2,5,6) 
 GROUP BY info.id)

Answer 1

使用ORDER BY或LIMIT子句对整个UNION进行排序或限制结果，括起单个SELECT语句并放置最后一个之后的ORDER BY或LIMIT。以下示例使用两者子句：
(SELECT a FROM t1 WHERE a=10 AND B=1)
UNION
(SELECT a FROM t2 WHERE a=11 AND B=2)
ORDER BY a LIMIT 10;

http://dev.mysql.com/doc/refman/5.5/en/union.html

Answer 2

您可以制作这样的子查询：

SELECT info.id
FROM
(
  (SELECT info.id 
   FROM info, 1_all 
   WHERE 1_all.id = info.id and 1_all.table_type = 'disp'  AND 1_all.year = '$year' AND     info.category IN (1,2,3) AND info.area IN (2,5,6)  
   GROUP BY resinfo.id ) 
  UNION ALL 
  (SELECT info.id 
   FROM info, 2_all 
   WHERE 2_all.id = info.id and 2_all.table_type = 'disp' AND 2_all.year = '$year' AND info.category IN (1,2,3) AND info.area IN (2,5,6) 
   GROUP BY info.id)
) as all
order by id desc;

Answer 3

我不知道MySQL引擎是否接受它，但SQL Server等其他引擎允许你在最后添加order by子句：

SELECT info.id 
 FROM info, 1_all 
 WHERE 1_all.id = info.id and 1_all.table_type = 'disp'  AND 1_all.year = '$year' AND      info.category IN (1,2,3) AND info.area IN (2,5,6)  
 GROUP BY resinfo.id
UNION ALL 
 SELECT info.id 
 FROM info, 2_all 
 WHERE 2_all.id = info.id and 2_all.table_type = 'disp' AND 2_all.year = '$year' AND     info.category IN (1,2,3) AND info.area IN (2,5,6) 
 GROUP BY info.id
ORDER BY info.id DESC;

如果您的数据库引擎不接受它，那么您最好的选择是根据您的联合查询创建一个视图，然后根据您的订单查询此视图。

你如何在MySQL中订购UNION？

3 个答案: