Question

我有下表Tble：

Name  |  Level
--------------
n1    |  L1
n1    |  L2
n2    |  L1
n2    |  L3
n3    |  L1
n4    |  L3

如何将SQL查询编写为输出？

Name  |  Level  
----------------
n1    |  L1_L2
n2    |  L1_L3
n3    |  L1
n4    |  L3

谢谢

Answer 1

假设MySQL：

SELECT Name, GROUP_CONCAT(Level SEPARATOR "_") Level
FROM tbl
GROUP BY Name

<强>结果

| NAME | LEVEL |
----------------
|   n1 | L1_L2 |
|   n2 | L1_L3 |
|   n3 |    L1 |
|   n4 |    L3 |

See the demo

Answer 2

所以，如果你的问题标题建议总是2行，那么就这样做：

SQL> select name,
  2         case
  3           when min(lvl)=max(lvl) then min(lvl)
  4           else min(lvl)||'_'||max(lvl)
  5         end lvl
  6    from data group by name
  7   order by name;

NA LVL
-- -----
n1 L1_L2
n2 L1_L3
n3 L1
n4 L3

在11g中，如果每个名称超过2行，则可以使用listagg：

SQL> select name,
  2         listagg(lvl, '_') within group (order by lvl) lvl
  3    from data
  4   group by name
  5   order by name;

NA LVL
-- --------------------
n1 L1_L2
n2 L1_L3
n3 L1
n4 L3

或10g：

SQL> select name,
  2         replace(wm_concat(lvl), ',', '_') lvl
  3    from data
  4   group by name
  5   order by name;

NA LVL
-- --------------------
n1 L1_L2
n2 L1_L3
n3 L1
n4 L3

Answer 3

这是Oracle 11g R2 解决方案：使用LISTAGG：

SELECT "Name", LISTAGG("Level", ',') WITHIN GROUP (ORDER BY "Level") "Levels"
FROM Table1 
GROUP BY "Name"
ORDER BY "Name";

SQL Fiddle

Answer 4

HSQLDB支持与MySQL相同的语法，但它使用SQL Standard单引号作为字符串常量。

SELECT "Name", GROUP_CONCAT("Level" ORDER BY "Level" SEPARATOR '_') "Level"
FROM "Tbl"
GROUP BY "Name"
ORDER BY "Name"

此示例假定您有引用的，大小写混合的表和列名称。

http://www.hsqldb.org/doc/2.0/guide/dataaccess-chapt.html#dac_aggregate_funcs

sql查询连接同一列的2行

4 个答案: