Question

我有一个表，它有7个不同的类，区域值。

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但是我希望以每个不同的pid | class| area | ----+------+------+ 2 | 1 | 10 | 2 | 2 | 10 | 2 | 6 | 20 | 4 | 1 | 30 | 4 | 2 | 40 | 4 | 3 | 50 | 4 | 4 | 60 | 4 | 5 | 70 | 9 | 6 | 80 | 11 | 1 | 90 | 11 | 4 | 10 | 11 | 7 | 20 |作为列标题的格式呈现此数据，然后让每行对应一个类区域（即第一行是每个{{1级的区域） 1}}）。

pid

是否可以在PostgreSQL中创建这样的输出？

Answer 1

试试这个：

SELECT 
    SUM(CASE WHEN pid = 2 THEN area ELSE 0 END) As "2",
    SUM(CASE WHEN pid = 4 THEN area ELSE 0 END) As "4",
    SUM(CASE WHEN pid = 9 THEN area ELSE 0 END) As "9",
    SUM(CASE WHEN pid = 11 THEN area ELSE 0 END) As "11"
FROM t
GROUP BY class
ORDER BY class

Postgres交叉表查询

1 个答案: