Question

我有一个选择查询，它将返回类似下表的内容：

start | stop | id
------------------
0     | 100  | 1
1     | 101  | 1
2     | 102  | 1
2     | 102  | 2
5     | 105  | 1
7     | 107  | 2
...
300   | 400  | 1
370   | 470  | 1
450   | 550  | 1

其中stop = start + n;在这种情况下，n = 100。

我想合并每个id的重叠：

start | stop | id
------------------
0     | 105  | 1
2     | 107  | 2
...
300   | 550  | 1

id 1不给0 - 550，因为开始300在停止105之后。

第一个查询将返回数十万条记录，n最多可达数万条，因此处理得越快越好。

使用PostgreSQL btw。

Answer 1

WITH    bounds AS
        (
        SELECT  *, ROW_NUMBER() OVER (PARTITION BY id ORDER BY start) AS rn
        FROM    (
                SELECT  id, LAG(stop) OVER (PARTITION BY id ORDER BY start) AS pstop, start
                FROM    q
                UNION ALL
                SELECT  id, MAX(stop), NULL
                FROM    q
                GROUP BY
                        id
                ) q2
        WHERE   start > pstop OR pstop IS NULL OR start IS NULL
        )
SELECT  b2.start, b1.pstop
FROM    bounds b1
JOIN    bounds b2
ON      b1.id = b2.id
        AND b1.rn = b2.rn + 1

减少SQL中的行

1 个答案: