Question

我一直在尝试对多个枢纽和多个列进行交叉分析

我怎么去

create table sales(year int, branch text, month int, qty int, scrap int, yield int);
insert into sales values(2007, 'Houston', 1, 1000, 66, 11);
insert into sales values(2007, 'Houston', 3, 1500, 55, 22);
insert into sales values(2007, 'Austin',  3,  500, 44, 33);
insert into sales values(2007, 'Laredo',  2, 1500, 77, 44);
insert into sales values(2007, 'El Paso', 2, 2000, 88, 55);
insert into sales values(2008, 'Waco',    1,  900, 99, 66);

像这样交叉表

 year | branch  | jan_qty | jan_scr | jan_yld | feb_qty | feb_scr | feb_yld | mar_qty | mar_scr | mar_yld
------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------
 2007 | Austin  |         |         |         |         |         |         |     500 |      44 |      33     
 2007 | El Paso |         |         |         |    2000 |      88 |      55 |         |         |     
 2007 | Houston |    1000 |      66 |      11 |         |         |         |    1500 |      55 |      22
 2007 | Laredo  |         |         |         |    1500 |      77 |      44 |         |         | 
 2008 | Waco    |     900 |      99 |      66 |         |         |         |         |         |

年份和分支都是支点，每个月包含3个值？

Answer 1

1。最简单的路线

可能是以下情况。它不是 DRY ，但它可以完成此工作，而且可读性强，可用于任何SQL风格，并且可以轻松地由应用程序代码生成。

SELECT
  grain.year,
  grain.branch,
  (SELECT qty FROM sales WHERE sales.year = grain.year AND sales.branch = grain.branch AND sales.month = 1) AS jan_qty,
  (SELECT scr FROM sales WHERE sales.year = grain.year AND sales.branch = grain.branch AND sales.month = 1) AS jan_scr,
  (SELECT yld FROM sales WHERE sales.year = grain.year AND sales.branch = grain.branch AND sales.month = 1) AS jan_yld,
  ... same for feb ...,
  ... same for mar ...
FROM (SELECT DISTINCT year, branch FROM sales) grain

应用程序代码只需要列jan_qty，jan_scr ...的名称即可通过简单的循环生成此SQL。

我将确保EXPLAIN ANALYZE以上查询来检查PostgreSQL是否有效地运行了该查询。

2。美丽的路线

这是一个数据透视表，PostgreSQL为我们提供了CROSSTAB函数来进行这种查询。 This post完美地解释了如何做到这一点，包括如何处理缺失值（即结果表中的空单元格），在您提供的示例中就是这种情况

多枢纽和多栏上的Postgresql交叉表

1 个答案: