Question

我想在交叉表中查询此查询的结果：

SELECT district, sex ,count(sex)
FROM table1
GROUP BY sex, district
ORDER BY district;

district | sex | count
---------+-----+-----
dis_1    | M   | 2
dis_1    | F   | 4
dis_1    | NI  | 1
dis_2    | M   | 5
dis_2    | F   | 2

像这样：

district | M | F | NI
---------+---+---+---
dis_1    | 2 | 4 | 1
dis_2    | 5 | 2 | 0

我做了一些测试没有成功，如下面的查询：

SELECT  row_name AS district,
        category_1::varchar(10) AS m,
        category_2::varchar(10) AS f,
        category_3::varchar(10) AS ni,
        category_4::int AS count

FROM crosstab('select district, sex, count(*)
               from table1 group by district, sex')
     AS ct  (row_name varchar(27), 
             category_1 varchar(10), 
             category_2 varchar(10), 
             category_3 varchar(10),
             category_4 int);

Answer 1

此交叉表功能完全按照您的要求生成（简化数据类型除外）：

SELECT *
FROM   crosstab('
         SELECT district, sex, count(*)::int
         FROM   table1
         GROUP  BY 1,2
         ORDER  BY 1,2'
        ,$$VALUES ('M'), ('F'), ('NI')$$)
AS ct (district text
      ,"M"      int
      ,"F"      int
      ,"NI"     int);

您尝试时遇到了一些错误在这个密切相关的答案中查找详细信息和解释：
PostgreSQL Crosstab Query

Answer 2

您可以使用带有CASE表达式的聚合函数来获得列中的结果：

select district,
  sum(case when sex ='M' then 1 else 0 end) M,
  sum(case when sex ='F' then 1 else 0 end) F,
  sum(case when sex ='NI' then 1 else 0 end) NI
from table1
group by district
order by district

PostgreSQL中的交叉表查询

2 个答案: