Question

我正在使用Enterprise Edition版本11.2.0.4.0。我想将表中的每个学生的注释连接成一个巨大的注释，然后将其输出（假脱机）到文件中。

我的表TEACHER_COMMENTS有列：

SID  INT
COMMENTS VARCHAR2(4000)

数据如下所示：

SID   COMMENTS
1    It has truly been a pleasure getting to know your child this quarter. our child has made great progress across the curriculum since the beginning of the school year.
1    Your child has done a very nice job this quarter, taking pride in her work and completing assignments with quality in mind.. Your child has made very good academic and/or social progress this quarter.

我想将同一个学生的评论合并为一个巨大的评论。

这是我的代码：

SET ECHO OFF NEWP 0 SPA 0 PAGES 0 FEED OFF HEAD OFF TRIMS ON
set underline off
set pages 0
set lines 1500
set feedback off
set autop off
set term off
set ver off
set timing off
set time off

spool E:\Test\Comments.csv

SELECT wm_concat(COMMENTS) FROM  TEACHER_COMMENTS t GROUP BY SID;

spool off;

exit;

这只是输出一行评论，而不是整个巨大的评论。

我也尝试过使用LIST_AGG

SELECT LISTAGG(COMMENT, ' ') WITHIN GROUP (ORDER BY COMMENT) AS All_Comments
FROM  TEACHER_COMMENTS t
GROUP BY SID

这会引发错误：

ORA-01489: result of string concatenation is too long

我该怎么做？请帮忙。

Answer 1

ORA-01489：字符串连接的结果太长

LISTAGG 返回VARCHAR2 (or RAW)，因此限制为4000字节。默认情况下，SQL*Plus的行大小为80。

一种可能的解决方案是使用XMLAGG并将LONG设置为较高的值。让我们看看它是如何运作的 -

SQL> SET LONG 2000000000
SQL> WITH DATA AS(
  2  SELECT 1 SID, 'It has truly been A pleasure getting TO know your CHILD
  3  this quarter. our CHILD has made great progress across THE curriculum
  4  since THE beginning OF THE school YEAR.' comments FROM dual UNION ALL
  5  SELECT 1, 'Your child has done a very nice job this quarter, taking pride
  6  in her work and completing assignments with quality in mind.. Your child
  7  has made very good academic and/or social progress this quarter.' FROM dual
  8  )
  9  SELECT rtrim(xmlagg(XMLELEMENT(e,comments,',').EXTRACT('//text()')
 10  ORDER BY sid).GetClobVal(),',') as long_comments
 11  FROM DATA
 12  /

LONG_COMMENTS
--------------------------------------------------------------------------------
It has truly been A pleasure getting TO know your CHILD
this quarter. our CHILD has made great progress across THE curriculum
since THE beginning OF THE school YEAR.,Your child has done a very nice job this
 quarter, taking pride
in her work and completing assignments with quality in mind.. Your child
has made very good academic and/or social progress this quarter.


SQL>

Answer 2

由于你有11.2，你应该可以使用listagg。

SELECT LISTAGG(comments, ',') WITHIN GROUP (ORDER BY sid) AS BIGCOMMENT
FROM   teacher_comments
GROUP BY sid;

我不记得listagg是否返回clob，但如果确实如此，我会在使用上面的SQL之前遵循Jon Heller的建议。你肯定想停止使用wm_concat。

连接来自同一列Oracle 11G的大量文本数据

2 个答案: