SQL查询以特定顺序发生的事件

Question

我有下表：

+--------+-------+------+--+
| Object | Event | Time |  |
+--------+-------+------+--+
| Obj1   | A     |    1 |  |
| Obj1   | B     |    3 |  |
| Obj2   | A     |    7 |  |
| Obj2   | B     |    4 |  |
+--------+-------+------+--+

我的目标是让所有具有事件A和B的对象具有A首先发生的条件（及时）。 到目前为止，我只想出了查询，找到了所有包含A＆B而没有包含时间的对象：

SELECT DISTINCT Object 
FROM
    (SELECT * 
     FROM
         (SELECT * 
          FROM table
          INNER JOIN 
              (SELECT Object Obj 
               FROM table 
               WHERE event LIKE '%A%' AS temp_table) ON table.Object = temp_table.Obj) AS temp_final 
     WHERE event LIKE '%B%') AS temp2;

所以最终结果是我得到的表只包括：

Obj1

因为这是唯一符合所有标准的对象。

时间列是现实生活中的日期标记，但为简单起见，我使用了整数。

谢谢你的帮助

Answer 1

如果您只跟踪一个接一个发生的两个事件，那么您可以通过一个JOIN来解决这个问题。

无论Obj1有多少事件，这都会有效，正如你所提到的，你只对A和B存在感兴趣并且分别对一个接一个感兴趣。

select distinct t1.object
from TABLE t1
    inner join TABLE t2 on t1.object = t2.object
        and t2.time > t1.time
        and t1.event = 'A'
        and t2.event = 'B'

以下是代码结果的示例：

declare @tbl table (obj varchar(10), event varchar(1), time int)

insert @tbl values ('Obj1', 'A', 1), ('Obj1', 'B', 3), ('Obj2', 'A', 7), ('Obj2', 'B', 4)

select distinct t1.obj
from @tbl t1
    inner join @tbl t2 on t1.obj = t2.obj
        and t2.time > t1.time
        and t1.event = 'A'
        and t2.event = 'B'

Answer 2

这是一个紧凑的解决方案，应该在大多数RDBMS上运行。 此解决方案不假设只有两个事件，并且应该针对任意数量的事件运行。

SELECT t1.Object
FROM yourTable t1
INNER JOIN
(
    SELECT Object, MIN(Time) AS Time
    FROM yourTable
    GROUP BY Object
) t2
    ON t1.Object = t2.Object AND
       ((t1.Event = 'A' AND t1.Time = t2.Time) OR
        t1.Event <> 'A')
GROUP BY t1.Object
HAVING COUNT(*) = 2    -- change this count to match # of events

MySQL演示：

SQLFiddle

Answer 3

尝试这个：

SELECT DISTINCT object
FROM yourtable t
WHERE EXISTS
    (SELECT FROM yourtable t3
    WHERE t3.object = t.object
    AND t3.event = 'A'
    AND EXISTS
        (SELECT 'B'
        FROM yourtbale t4
        WHERE t4.object = t3.object
        AND t4.event = 'B'
        AND t4.time > t3.time)
   )

Answer 4

如果您使用的是sql-server：

SELECT
      A.[Object]
    , A.[Time]
    , B.[Time]
FROM
    (SELECT 
        Distinct [Object]
    FROM
        [table] AS A
    WHERE
        A.[Event] = 'A'
    ) AS A
        CROSS APPLY
    (SELECT
        TOP 1 *
    FROM
        [table] AS B
    WHERE
        [Event] = 'B'
        AND
        B.[Object] = A.[Object]
        AND
        A.[Time] < B.[Time]) AS B

Answer 5

对于SQL Server：

;with A as
(select Object, MIN(Time) as Time from table where Event='A' group by Object)
, B as
(select Object, MIN(Time) aS Time from table where Event='B' group by Object)
Select A.Object from A inner join B on B.Object=A.Object where A.Time < B.Time