我想生成一个日期列表,希望与另一个表连接,但我不知道要使用什么语法,类似于这样:
SELECT dates.date, transactions.account_id, transactions.amount
FROM (...) as dates
LEFT JOIN transactions ON transactions.date = dates.date
WHERE dates.date >= '2010-01-01' AND dates.date <= '2010-12-31'
ORDER BY dates.date;
我想要日期,这样我就不必在客户端进一步处理数据了。我正在使用它来显示与此类似的表格:
Account 2010-01-01 2010-01-02 2010-01-03 Balance
============================================================
Chase 123 +100 -20 -70 +10
Chase 231 +13 -9 +4
最佳答案
日期列表
使用 generate_series function获取可以添加到日期以获取日期列表的数字列表:
SELECT CURRENT_DATE + s.a AS dates
FROM generate_series(0,14,7) as s(a);
结果:
dates
------------
2004-02-05
2004-02-12
2004-02-19
旋转
问题的后半部分涉及对结果集进行透视——将行数据转换为列数据。 PIVOT 和 UNPIVOT 是 ANSI,但我不认为它们是 supported by PostgreSQL currently .最一致支持的旋转查询的方法是使用聚合函数:
SELECT t.account,
SUM(CASE WHEN t.date = '2010-01-01' THEN t.amount END) AS '2010-01-01',
SUM(CASE WHEN t.date = '2010-01-02' THEN t.amount END) AS '2010-01-02',
SUM(CASE WHEN t.date = '2010-01-03' THEN t.amount END) AS '2010-01-03',
SUM(t.amount) AS Balance
FROM (SELECT CURRENT_DATE + s.a AS dates
FROM generate_series(0,14,7) as s(a)) x
LEFT JOIN TRANSACTIONS y ON y.date = x.date
GROUP BY t.account
动态列
...表示dynamic SQL .
关于sql - 如何生成虚拟表以在 PostgreSQL 中生成日期序列?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/4002029/