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crosstab()我在使用该函数在 PostgreSQL 中创建数据透视表时遇到问题。它工作得很好,但它会为同一个文件生成多个记录client_id。我怎样才能避免这种情况?

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

感谢 Erwin,它现在可以工作了,但我试图在没有内置功能的情况下做到这一点,但没有运气。有人可以对此提出建议吗?我的代码只有两年:

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;
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1 回答 1

3

您需要ORDER BY相应地进行第一个查询。我在这里使用简化的语法 ORDER BY <ordinal number>

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()函数不包含在标准 PostgreSQL 中,但带有附加模块 tablefunc

编辑附加请求

没有crosstab()功能的版本:仅分组,client_id否则您最终会得到多行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;
于 2011-11-06T18:11:25.607 回答