怎么把两列合并成一列，相同的字段，不用合并

[iiiiiiiii_z]

通过全连接，查询出来的结果集，怎么把第一列和第二列合并一起，相同的字段不用合并。

[吉普赛的歌]

你这个其实只有三种情况： 1. 两列 areaid 相同; 2. 两列 areaid 均为null; 3. 两列 areaid 有一列为 null; mysql 用 ifnull 就可以了吧：

SELECT ifnull(m.areaid,n.areaid) AS `areaid`
      ,m.a2
      ,n.a3
FROM   (
           SELECT c.areaid AS areaidrb.zzdzje AS a2
           FROM   dsass_zwb_fjkffwxq a
                  LEFT JOIN dsassfjfjpsdjb b
                       ON  a.ida_psdj = b.id
                  LEFT JOIN dsassfjfjfwhfb c
                       ON  a.ida_hfb = c.id
           WHERE  a.chaptertype = '1'
       )m
       FULL JOIN (
                SELECT c.areaid AS areaidrb.zzdzje AS a3 |
                FROM   dsass_zwb_fjkffwxq a
                       LEFT JOIN dsassfjfjpsdjb b
                            ON  a.id_psdj = b.id
                       LEFT JOIN dsassfjfjfwhfb c
                            ON  a.id_hfb = c.id
                WHERE  a.chaptertype = '2'
            )n
            ON  m.areaid = n.areaid

sqlserver:

SELECT COALESCE(m.areaid,n.areaid) AS [areaid]
      ,m.a2
      ,n.a3
FROM   (
           SELECT c.areaid AS areaidrb.zzdzje AS a2
           FROM   dsass_zwb_fjkffwxq a
                  LEFT JOIN dsassfjfjpsdjb b
                       ON  a.ida_psdj = b.id
                  LEFT JOIN dsassfjfjfwhfb c
                       ON  a.ida_hfb = c.id
           WHERE  a.chaptertype = '1'
       )m
       FULL JOIN (
                SELECT c.areaid AS areaidrb.zzdzje AS a3 |
                FROM   dsass_zwb_fjkffwxq a
                       LEFT JOIN dsassfjfjpsdjb b
                            ON  a.id_psdj = b.id
                       LEFT JOIN dsassfjfjfwhfb c
                            ON  a.id_hfb = c.id
                WHERE  a.chaptertype = '2'
            )n
            ON  m.areaid = n.areaid

[qq_41911785]

楼上的,SQL server 用isnull()就行了

[二月十六]

 SELECT COALESCE(m.arreaid,n.areaid) AS areaid,m.a2,n.a3.......

[iiiiiiiii_z]

引用 1 楼 yenange 的回复:

你这个其实只有三种情况：
1. 两列 areaid 相同;
2. 两列 areaid 均为null;
3. 两列 areaid 有一列为 null;

mysql 用 ifnull 就可以了吧：

SELECT ifnull(m.areaid,n.areaid) AS `areaid`
      ,m.a2
      ,n.a3
FROM   (
           SELECT c.areaid AS areaidrb.zzdzje AS a2
           FROM   dsass_zwb_fjkffwxq a
                  LEFT JOIN dsassfjfjpsdjb b
                       ON  a.ida_psdj = b.id
                  LEFT JOIN dsassfjfjfwhfb c
                       ON  a.ida_hfb = c.id
           WHERE  a.chaptertype = '1'
       )m
       FULL JOIN (
                SELECT c.areaid AS areaidrb.zzdzje AS a3 |
                FROM   dsass_zwb_fjkffwxq a
                       LEFT JOIN dsassfjfjpsdjb b
                            ON  a.id_psdj = b.id
                       LEFT JOIN dsassfjfjfwhfb c
                            ON  a.id_hfb = c.id
                WHERE  a.chaptertype = '2'
            )n
            ON  m.areaid = n.areaid

sqlserver:

SELECT COALESCE(m.areaid,n.areaid) AS [areaid]
      ,m.a2
      ,n.a3
FROM   (
           SELECT c.areaid AS areaidrb.zzdzje AS a2
           FROM   dsass_zwb_fjkffwxq a
                  LEFT JOIN dsassfjfjpsdjb b
                       ON  a.ida_psdj = b.id
                  LEFT JOIN dsassfjfjfwhfb c
                       ON  a.ida_hfb = c.id
           WHERE  a.chaptertype = '1'
       )m
       FULL JOIN (
                SELECT c.areaid AS areaidrb.zzdzje AS a3 |
                FROM   dsass_zwb_fjkffwxq a
                       LEFT JOIN dsassfjfjpsdjb b
                            ON  a.id_psdj = b.id
                       LEFT JOIN dsassfjfjfwhfb c
                            ON  a.id_hfb = c.id
                WHERE  a.chaptertype = '2'
            )n
            ON  m.areaid = n.areaid

非常感谢，你打了这么多，我下次注意一下，语句复制出来。

[吉普赛的歌]

引用 4 楼 u011002950 的回复:

非常感谢，你打了这么多，我下次注意一下，语句复制出来。

不客气， 没事就结贴吧。