使用交叉表功能的PostgreSQL和数据透视表 [英] PostgreSQL and pivot tables using crosstab function

问题描述

我在使用crosstab()函数在PostgreSQL中创建数据透视表时遇到问题.它运作良好，但会为同一client_id产生多个记录.如何避免这种情况?

I have a problem with creating a pivot table in PostgreSQL using the crosstab() function. It works well but it produces multiple records for the same client_id. How can I avoid this?

这是SQL:

SELECT *
FROM crosstab('SELECT client_id
                     ,extract(year from date)
                     ,sum(amount)
               from   orders
               group  by extract(year from date)
                     ,client_id'
             ,'SELECT extract(year from date)
               FROM   orders
               GROUP  BY extract(year from date)
               order  by extract(year from date)')
AS orders(
row_name integer,
year_2001 text,
year_2002 text,
year_2003 text,
year_2004 text,
year_2005 text,
year_2006 text,
year_2007 text,
year_2008 text,
year_2009 text,
year_2010 text,
year_2011 text);

//编辑

Thx to Erwin现在可以使用了，但是我试图在没有内置函数的情况下做到这一点，但是没有运气.有人可以提出建议吗?我的代码只有两年了:

Thx to Erwin it works now, but I have tried to do this without built in function with no luck. Can someone suggest something on that? My code for only two years:

SELECT DISTINCT o.client_id,
       CASE WHEN (extract(year from o.date)=2001)
            THEN sum(o.amount) ELSE 0 END,
       CASE WHEN (extract(year from o.date)=2002)
            THEN sum(o.amount) ELSE 0 END
FROM orders AS o
GROUP BY 1, extract(year from o.date)
ORDER BY 1;

推荐答案

您需要相应地ORDER BY第一个查询.我在这里使用简化语法 ORDER BY <ordinal number>

You need to ORDER BY the first query accordingly. I use the simplified syntax ORDER BY <ordinal number> here.

SELECT *
FROM   crosstab(
        'SELECT client_id
               ,extract(year from date)
               ,sum(amount)
         FROM   orders
         GROUP  BY 1,2
         ORDER  BY 1,2',

        'SELECT extract(year from date)
         FROM   orders
         GROUP  BY 1
         ORDER  BY 1')
AS orders(
    row_name integer,
    year_2001 text,
    year_2002 text,
    year_2003 text,
    year_2004 text,
    year_2005 text,
    year_2006 text,
    year_2007 text,
    year_2008 text,
    year_2009 text,
    year_2010 text,
    year_2011 text);

crosstab()函数未包含在标准PostgreSQL中，但随附了其他功能模块tablefunc .

The crosstab() function is not included in standard PostgreSQL but comes with the additional module tablefunc.

没有crosstab()功能的版本: 仅按client_id分组，否则每个client_id最终将有多行.

Version without crosstab() function: Only group by client_id or you will end up with multiple rows per client_id.

SELECT client_id
      ,sum(CASE WHEN extract(year from date) = 2001 THEN amount ELSE 0 END) AS year_2001
      ,sum(CASE WHEN extract(year from date) = 2002 THEN amount ELSE 0 END) AS year_2002
       -- ...
FROM   orders o
GROUP  BY 1
ORDER  BY 1;

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