如何使用SQL按另一列中的值聚合一列中的数据

我在PostgreSQL中有一个表，其中包含我国每个省份的人口统计数据

Columns are: Province_name, professions, Number_of_people.

正如你所看到的，每个职业的省名都是重复的。

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那么，我如何才能不重复省份名称，而是在单独的列中获取专业名称呢？

您想要做的是在Postgresql中比在其他rdbms中更复杂一点的透视。您可以使用交叉表功能。请在此处查找介绍：

对你来说，它看起来像这样：

SELECT * 
FROM crosstab( 'select Province_name, professions, Number_of_people from table1 order by 1,2') 
     AS final_result(Province_name TEXT, data_scientist NUMERIC,data_engineer NUMERIC,data_architect NUMERIC,student NUMERIC);

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听起来好像你想改变你的表（真的：最好在你的问题中显示数据和预期的输出！）

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这是使用

FILTER

子句实现这一点的PostgreSQL方法（从9.4开始）

SELECT
    province,
    SUM(people) FILTER (WHERE profession = 'teacher') AS teacher,
    SUM(people) FILTER (WHERE profession = 'banker') AS banker,
    SUM(people) FILTER (WHERE profession = 'supervillian') AS supervillian
FROM mytable
GROUP BY province

SELECT
    province,
    SUM(CASE WHEN profession = 'teacher' THEN people ELSE 0 END) AS teacher,
    SUM(CASE WHEN profession = 'banker' THEN people ELSE 0 END) AS banker,
    SUM(CASE WHEN profession = 'supervillian' THEN people ELSE 0 END) AS supervillian
FROM mytable
GROUP BY province

如果您想采用更常见的方法，可以使用

CASE

子句

SELECT
    province,
    SUM(people) FILTER (WHERE profession = 'teacher') AS teacher,
    SUM(people) FILTER (WHERE profession = 'banker') AS banker,
    SUM(people) FILTER (WHERE profession = 'supervillian') AS supervillian
FROM mytable
GROUP BY province

SELECT
    province,
    SUM(CASE WHEN profession = 'teacher' THEN people ELSE 0 END) AS teacher,
    SUM(CASE WHEN profession = 'banker' THEN people ELSE 0 END) AS banker,
    SUM(CASE WHEN profession = 'supervillian' THEN people ELSE 0 END) AS supervillian
FROM mytable
GROUP BY province

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请以表格形式提供您的示例数据和预期输出（通过单击下面的链接）并根据该数据添加一些示例数据和预期输出。请（您的问题-请勿在评论中发布代码或其他信息）Sry，我们没有看到任何内容。请添加示例数据和预期输出！这正是我想要的。我最终在Excel中将数据导出为CSV和do pivot表。谢谢你的关注！