Question

我有一张这样的表：

name    id1     id2     id3     id4
Mark    aaa     null    null    null
Mark    null    bbb     null    null
Mark    null    null    null    null
John    null    null    eee     null
John    ccc     null    null    null
John    null    ddd     null    null
John    null    null    null    null

所以，我有5列，名称，id1，id2，id3和id4 -all是字符串值。我只需要一个GROUP BY的名字;除了null值之外，它将包含所有值。所以最终输出将是这样的：

    name    id1     id2     id3     id4
    Mark    aaa     bbb     null    null
    John    ccc     ddd     eee     null

有人可以帮我这么做吗？

Answer 1

Use MAX:

SELECT
    name,
    MAX(id1) AS id1,
    MAX(id2) AS id2,
    MAX(id3) AS id3,
    MAX(id4) AS id4
FROM tbl
GROUP BY name;

Answer 2

使用类似的东西：

select 
  name,
  max(id1) id1,
  max(id2) id2,
 max(id3) id3,
  max(id4) id4
from
(
  select name, id1, id2, id3, id4,
    row_number() over(partition by name
                      order by name) seq
  from yourtable
) d
group by name

Answer 3

字符串上的最大值... Z大于A.任何字符串都大于null。别忘了GROUP BY

create table #test(
name varchar(10),
id1 varchar(10),
id2 varchar(10),
id3 varchar(10),
id4 varchar(10)
)

INSERT INTO #test SELECT 'Mark', 'aaa', null, null, null;
INSERT INTO #test SELECT 'Mark', null, 'bbb', null, null;
INSERT INTO #test SELECT 'Mark', null, null, null, null
INSERT INTO #test SELECT 'John', null, null, 'eee', null
INSERT INTO #test SELECT 'John', 'ccc', null, null, null
INSERT INTO #test SELECT 'John', null, 'ddd', null, null
INSERT INTO #test SELECT 'John', null, null, null, null

SELECT
    name,
    MAX(id1) AS id1,
    MAX(id2) AS id2,
    MAX(id3) AS id3,
    MAX(id4) AS id4
FROM #test
Group By name

drop table #test

SQL：GROUP BY有一列

3 个答案: