用于连接 Oracle 中多行列值的 SQL 查询

2021-12-01 00:00:00 sql oracle string-aggregation

是否可以构造 SQL 来连接来自多行?

以下是一个例子:

表A

<前>PID一种乙C

表 B

<前>PID 序列描述A 1 有A 2 不错一个3天.B 1 干得漂亮.C 1 是C 2 我们可以C 3 做C 4 这个作品！

SQL 的输出应该是 -

<前>PID 描述A 祝你有美好的一天.B 干得好.C 是的，我们可以完成这项工作！

所以基本上输出表的 Desc 列是表 B 中 SEQ 值的串联?

对 SQL 有任何帮助吗?

解决方案

根据您的版本，有几种方法 - 请参阅关于字符串聚合技术的 oracle 文档.一个很常见的方法是使用 LISTAGG:

SELECT pid, LISTAGG(Desc, ' ') WITHIN GROUP (ORDER BY seq) AS 描述FROM B GROUP BY pid;

然后加入A来挑选你想要的pids.

注意:开箱即用，LISTAGG 仅适用于 VARCHAR2 列.

Would it be possible to construct SQL to concatenate column values from multiple rows?



The following is an example: 

Table A
PID
A
B
C
Table B
PID   SEQ    Desc

A     1      Have
A     2      a nice
A     3      day.
B     1      Nice Work.
C     1      Yes
C     2      we can 
C     3      do 
C     4      this work!
Output of the SQL should be -
PID   Desc
A     Have a nice day.
B     Nice Work.
C     Yes we can do this work!
So basically the Desc column for out put table is a concatenation of the SEQ values from Table B?

Any help with the SQL?
 解决方案 There are a few ways depending on what version you have - see the oracle documentation on string aggregation techniques. A very common one is to use LISTAGG:
SELECT pid, LISTAGG(Desc, ' ') WITHIN GROUP (ORDER BY seq) AS description
FROM B GROUP BY pid;
Then join to A to pick out the pids you want.

Note: Out of the box, LISTAGG only works correctly with VARCHAR2 columns.


	
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