如何使此 CTE 查询打印值为 0 的行？

Question

我有一个基于 CTE 的查询，我使用连接传递了大约 2600 个 4 元组纬度/经度值 - 这些纬度经度 4 元组已被 ID 标记并保存在名为坐标的第二个表中。这些左上角和右下角的纬度/经度值被传递到 CTE，以显示给定两个时间戳在这些坐标内发出的请求数量（每小时）。-我能够在时间戳内获得每天的总请求数给定，即每个指定日期的用户请求总数。 （例如，用户选择每周三或周三和周四等查看 - 在 2012 年 1 月 1 日至 31 日期间的 11:55 至 22:04 小时之间，对于我通过的每个纬度/经度 4 元组。）但我无法获得行结果中 zcount 为 0 时，我只得到 zcount > 0 的行。我的查询如下：（给Erwin Brandstetter 的注释如果他看到了这个，我检查了关于我之前的问题的聊天室讨论并设置了@ 987654322@ 值 NOT NULL 因为你说坐标可以设计为null，但我仍然有同样的问题。-虽然我可能已经理解了你的意思，因为我遇到了一个糟糕的情况那时候发烧-

WITH v AS (
   SELECT '2012-1-1 11:55:11'::timestamp AS _from -- provide times once
         ,'2012-1-31 22:02:21'::timestamp AS _to
   )
, q AS (
   SELECT c.coordinates_id
        , date_trunc('hour', t.calltime) AS stamp
        , count(*) AS zcount
   FROM   v
   JOIN   mytable t ON  t.calltime BETWEEN v._from AND v._to
                   AND (t.calltime::time >= v._from::time AND
                        t.calltime::time <= v._to::time) AND 
(extract(DOW from t.calltime) = 3)
   JOIN   coordinates c ON (t.lat, t.lon) 
                   BETWEEN (c.bottomrightlat, c.topleftlon)
                       AND (c.topleftlat, c.bottomrightlon)
   GROUP BY c.coordinates_id, date_trunc('hour', t.calltime)
   )
, cal AS (
   SELECT generate_series('2012-1-1 11:00:00'::timestamp
                        , '2012-1-31 23:00:00'::timestamp
                        , '1 hour'::interval) AS stamp)
SELECT q.coordinates_id, cal.stamp::date, sum(q.zcount) AS zcount
FROM   v, cal
LEFT   JOIN q USING (stamp)
WHERE  extract(hour from cal.stamp) BETWEEN extract(hour from v._from)
                                        AND extract(hour from v._to)
AND    extract(DOW from cal.stamp) = 3 
AND    cal.stamp >= v._from
AND    cal.stamp <= v._to
GROUP  BY 1,2
ORDER  BY 1,2;

我在执行这个查询时得到的输出基本上是这样的（通常我有大约 10354 行返回，不包括 zcount 为 0 的行，为了相似，只提供了两个坐标）：

coordinates_id  | stamp      | zcount
1               ;"2012-01-04";      2
1               ;"2012-01-11";      3
1               ;"2012-01-18";      2
2               ;"2012-01-04";      2
2               ;"2012-01-11";      3
2               ;"2012-01-18";      2

但是，应该像这样，所有 zcount 为 0 的行也应该与 zcount 非零的行一起打印出来 - 例如1 月 25 日，对于 ID 为 1 和 2 的两个坐标，zcount 为 0 也应打印在示例的这一小部分中-：

coordinates_id  | stamp      | zcount
1               ;"2012-01-04";      2
1               ;"2012-01-11";      3
1               ;"2012-01-18";      2
1               ;"2012-01-25";      0
2               ;"2012-01-04";      2
2               ;"2012-01-11";      3
2               ;"2012-01-18";      2
2               ;"2012-01-25";      0

zcount 值比实际值大得多的更新版本。 -zcount 为 0 的行仍然没有显示-

WITH v AS (
   SELECT '2012-1-1 11:55:11'::timestamp AS _from -- provide times once
         ,'2012-1-31 22:02:21'::timestamp AS _to
   )
, q AS (
   SELECT c.coordinates_id
        , date_trunc('hour', t.calltime) AS stamp
        , count(*) AS zcount
   FROM   v
   JOIN   mytable t ON  t.calltime BETWEEN v._from AND v._to
                   AND (t.calltime::time >= v._from::time AND
                        t.calltime::time <= v._to::time) AND 
(extract(DOW from t.calltime) = 3)
   JOIN   coordinates c ON (t.lat, t.lon) 
                   BETWEEN (c.bottomrightlat, c.topleftlon)
                       AND (c.topleftlat, c.bottomrightlon)
   GROUP BY c.coordinates_id, date_trunc('hour', t.calltime)
   )
, cal AS (
   SELECT generate_series('2012-1-1 11:00:00'::timestamp
                        , '2012-1-31 23:00:00'::timestamp
                        , '1 hour'::interval) AS stamp)
, coordst AS ( 
   SELECT coordinates_id FROM coordinates)
SELECT q.coordinates_id, cal.stamp::date, COALESCE(sum(q.zcount),0) AS zcount
FROM   v, coordst, cal
LEFT   JOIN q USING (stamp)
WHERE  extract(hour from cal.stamp) BETWEEN extract(hour from v._from)
                                        AND extract(hour from v._to)
AND    extract(DOW from cal.stamp) = 3 
AND    cal.stamp >= v._from
AND    cal.stamp <= v._to
GROUP  BY 1,2
ORDER  BY 1,2;

Answer 1

您需要一个不同的坐标 ID 列表来执行正确的 CROSS JOIN。 1. 在 WITH 中添加另一个条目。 2. 将其添加到您的 JOIN（FROM v,cal, coords）中。 3. 你的 zcount 会显示为 NULL，所以 COALESCE 吧。

WITH v AS (
   SELECT '2012-1-1 11:55:11'::timestamp AS _from -- provide times once
         ,'2012-1-31 22:02:21'::timestamp AS _to
   )
, q AS (
   SELECT c.coordinates_id
        , date_trunc('hour', t.calltime) AS stamp
        , count(*) AS zcount
   FROM   v
   JOIN   mytable t ON  t.calltime BETWEEN v._from AND v._to
                   AND (t.calltime::time >= v._from::time AND
                        t.calltime::time <= v._to::time) AND 
(extract(DOW from t.calltime) = 3)
   JOIN   coordinates c ON (t.lat, t.lon) 
                   BETWEEN (c.bottomrightlat, c.topleftlon)
                       AND (c.topleftlat, c.bottomrightlon)
   GROUP BY c.coordinates_id, date_trunc('hour', t.calltime)
   )
, cal AS (
   SELECT generate_series('2012-1-1 11:00:00'::timestamp
                        , '2012-1-31 23:00:00'::timestamp
                        , '1 hour'::interval) AS stamp)
, coordst AS ( 
   SELECT DISTINCT coordinates_id FROM coordinates)
SELECT coordst.coordinates_id, cal.stamp::date, COALESCE(sum(q.zcount),0) AS zcount
FROM   v CROSS JOIN coordst CROSS JOIN cal
LEFT   JOIN q USING q.stamp = cal.stamp AND coordst.coordinates_id = q.coordinates_id
WHERE  extract(hour from cal.stamp) BETWEEN extract(hour from v._from)
                                        AND extract(hour from v._to)
AND    extract(DOW from cal.stamp) = 3 
AND    cal.stamp >= v._from
AND    cal.stamp <= v._to
GROUP  BY 1,2
ORDER  BY 1,2;