如何使用PostgreSQL将多行合并为一列? [英] How can I combine multiple rows into one column using PostgreSQL?
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问题描述
如何将多个结果合并到一列中?
How can I combine multiple results into one column?
例如,我的查询显示以下结果:
For example, my query displays this result:
internaldocid | document id | versionid | title | tagname
1146 | DOC-1146 | 2 | Press Release | tag1
1146 | DOC-1146 | 2 | Press Release | tag2
1146 | DOC-1146 | 2 | Press Release | tag3
我希望它显示以下结果:
I would like it to display this result:
internaldocid | document id | versionid | title | tagname
1146 | DOC-1146 | 2 | Press Release | tag1, tag2, tag3
这是我的SQL:
SELECT
cmsdocument.internaldocid,
cmsdocument.documentid,
cmsdocument.versionid,
cmsdocversion.title,
cmstag.tagname
FROM
public.cmsobjecttag,
public.cmstag,
public.cmsdocument,
public.cmsdocversion,
public.cmsuser
WHERE
cmsobjecttag.tagid = cmstag.tagid AND
cmsobjecttag.objectid = cmsdocument.internaldocid AND
cmsdocument.internaldocid = cmsdocversion.internaldocid AND
cmsdocument.userid = cmsuser.userid AND
cmsdocversion.state = 'published' AND
cmsobjecttag.objecttype = '102';
任何帮助将不胜感激。
推荐答案
从PostgreSQL版本9开始,只需使用 string_agg :
Since PostgreSQL version 9, this is done simply by using string_agg:
SELECT
cmsdocument.internaldocid,
cmsdocument.documentid,
cmsdocument.versionid,
cmsdocversion.title,
string_agg(cmstag.tagname, ',')
FROM
public.cmsobjecttag,
public.cmstag,
public.cmsdocument,
public.cmsdocversion,
public.cmsuser
WHERE
cmsobjecttag.tagid = cmstag.tagid AND
cmsobjecttag.objectid = cmsdocument.internaldocid AND
cmsdocument.internaldocid = cmsdocversion.internaldocid AND
cmsdocument.userid = cmsuser.userid AND
cmsdocversion.state = 'published' AND
cmsobjecttag.objecttype = '102'
GROUP BY
cmsdocument.internaldocid,
cmsdocument.documentid,
cmsdocument.versionid,
cmsdocversion.title
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