时间间隔内的SQL Select记录

Question

我有一张桌子，上面有一堆记录：

userID    testID    value    time
1         1001      2        2009-09-05 06:25:00
1         1001      4        2009-09-05 07:25:00
1         1001      2        2009-09-05 03:25:00
1         1002      5        2009-09-05 06:25:00
1         1002      6        2009-09-05 07:25:00
1         1002      4        2009-09-05 03:25:00

用户在时间x输入。 我想在入学的前X个小时内查询每个测试的最新值。 IE，如果他在3:25进入，并且我想要3小时内的最新值，我想返回

1         1001      2        2009-09-05 07:25:00
1         1002      5        2009-09-05 07:25:00

我不确定执行此操作的最佳方法，但是到目前为止，这是我尝试过的方法：

SELECT testID, value from table WHERE userID = 1 and 
    time <= timestamp 'enter_time' + INTERVAL '3 HOURS' as u INNER JOIN 
    (SELECT testID, max(time) as time from table WHERE time <= timestamp 
    'enter_time' + INTERVAL '3 HOURS' GROUP BY testID) as q 
    on u.itemid = q.itemid AND u.time = q.time

我为此收到语法错误，但是代码似乎正确。 有人可以帮我一下吗？

谢谢！

Answer 1

您需要将第一个查询包装在括号中。

(SELECT testID, value from table WHERE userID = 1 and 
    time <= timestamp 'enter_time' + INTERVAL '3 HOURS') as u INNER JOIN 
    (SELECT testID, max(time) as time from table WHERE time <= timestamp 
    'enter_time' + INTERVAL '3 HOURS' GROUP BY testID) as q 
    on u.itemid = q.itemid AND u.time = q.time