Question

我想合并来自两个不同表的结果，他们唯一的共同点就是名为date_mod的日期字段

下面的查询仅显示第一个select语句中的两列。未显示profile_id列。

有关如何调整它的任何帮助，以便我可以根据date_mod字段的顺序将这两个表的最新结果组合起来。

SELECT resume_id,  date_mod FROM resumes  ORDER BY date_mod 
UNION ALL 
SELECT profile_id, date_mod FROM profiles ORDER BY date_mod LIMIT 5

Answer 1

显示了profile_id，但是列只有一个标签 - 第一个选择的标签。

SELECT resume_id as id,  date_mod as date, 'resume' as type FROM resumes
UNION ALL 
SELECT profile_id, date_mod, 'profile' FROM profiles 
ORDER BY date 
LIMIT 5

Answer 2

试试这个：

SELECT *
FROM
    (SELECT resume_id as `ID`,  date_mod
    FROM resumes
         UNION
    SELECT profile_id as `ID`, date_mod
    FROM profiles) iResult 
ORDER BY iResult.date_mod
LIMIT 5

Answer 3

我认为限制5导致您应该包装查询的问题，即

SELECT * FROM (SELECT resume_id,date_mod FROM resumes ORDER BY date_mod UNION ALL SELECT profile_id, date_mod FROM profiles ORDER BY date_mod) LIMIT 5

这应该提供你想要的东西

Answer 4

您应该在合并基础上申请订单：

(SELECT resume_id,  date_mod FROM resumes 
UNION ALL 
SELECT profile_id, date_mod FROM profiles ) ORDER BY date_mod LIMIT 5

Answer 5

执行UNION时，列必须具有相同的“别名”列结果和数据类型才能符合条件。如果你想要前五名，你应该实际应用两个限制来从两边获得MOST 5。然后应用OVERALL Limit 5，这样您就不会从两个单独的文件中预先返回所有记录

select 
      Source,
      SrcID,
      Date_Mod
   from
      ( SELECT 
              "R" as Source,
              resume_id as SrcID,
              date_mod 
           FROM 
              resumes
           ORDER BY 
              date_mod 
           LIMIT 5
        UNION ALL
        SELECT
              "P" as Source,
              profile_id as SrcID,
              date_mod
           FROM 
              profiles 
           ORDER BY 
              date_mod 
           LIMIT 5 ) PreQuery
   order by
      Date_Mod
   LIMIT 5

MYSQL UNION产生意外结果和缺少列

5 个答案: