我有TableA
和Table
B,如下所示。当前,正如您在下面的查询中所看到的,TableA
基于TableB
并与box_id
中的所有行相连接,这些行的TableB
在timestamp
TableA
的1分钟内。
我想修改此查询,以便代替选择timestamp
行1分钟以内的TableB
行,我想选择具有TableA
等效项或TableB
行的timestamp
行]最接近+小于timestamp
中的timestamp
。
以下是TableA
和TableA
以及我想要的TableB
的示例。一旦实现,就不再需要按Desired Table
分组。任何想法/帮助将不胜感激。
TableA:
rainfall, hail, weather
TableB:
id box_id timestamp
373001645 1 2020-05-07 06:00:20
373001695 1 2020-05-07 06:02:26
373001762 1 2020-05-07 06:05:17
373001794 1 2020-05-07 06:06:38
373001810 2 2020-05-07 06:07:21
所需表:
id box_id timestamp data
373001345 1 2020-05-07 06:00:20 {"R": 0.114, "H": 20.808}
373001395 1 2020-05-07 06:02:26 {"R": 0.12, "H": 15.544}
373001462 1 2020-05-07 06:03:01 {"R": 0.006, "H": 55.469}
373001494 1 2020-05-07 06:04:38 {"R": 0.004, "H": 51.85}
373001496 1 2020-05-07 06:05:18 {"R": 0.02, "H": 5.8965}
373001497 1 2020-05-07 06:06:39 {"R": 0.12, "H": 54.32}
373001510 2 2020-05-07 06:07:09 {"R": 0.34, "H": 1.32}
373001511 2 2020-05-07 06:07:29 {"R": 0.56, "H": 32.7}
查询:
id timestamp rainfall hail weather
373001345 2020-05-07 06:00:20 0.114 20.808 {"Rainfall": 0.114, "Hail": 20.808}
373001395 2020-05-07 06:02:26 0.12 15.544 {"Rainfall": 0.12, "Hail": 15.544}
373001462 2020-05-07 06:05:17 0.004 51.85 {"Rainfall": 0.004, "Hail": 51.85}
373001494 2020-05-07 06:06:38 0.02 5.8965 {"Rainfall": 0.02, "Hail": 5.8965}
373001496 2020-05-07 06:07:21 0.34 1.32 {"Rainfall": 0.34, "Hail": 1.32}
您可以在SELECT tableA.id, tableA.timestamp AS timestamp,
(tableB.data->'$.R') as rainfall, (tableB.data->'$.H') as hail,
JSON_OBJECT("Hail", (tableB.data->'$.H'),"Rainfall", (tableB.data->'$.R')) AS weather
FROM tableA tableA
LEFT JOIN tableB tableB ON tableA.box_id = tableB.box_id
AND TIMESTAMPDIFF(MINUTE, tableB.timestamp, tableA.timestamp) BETWEEN -1 AND 1
WHERE
tableA.timestamp BETWEEN '2020-05-07 00:00:00' AND '2020-05-07 23:59:59'
GROUP BY tableA.id,rainfall,hail,weather
ORDER BY tableA.timestamp ASC;
条件下使用相关子查询,以在ON
中查找最大timestamp
,该最大值小于或等于tableB
中的当前行时间戳,并基于此:tableA
:] >
JOIN
输出:
SELECT A.id, A.timestamp AS timestamp, B.data->'$.R' as rainfall, B.data->'$.H' as hail, JSON_OBJECT("Hail", B.data->'$.H', "Rainfall", B.data->'$.R' ) AS weather FROM tableA A LEFT JOIN tableB B ON B.box_id = A.box_id AND B.timestamp = (SELECT MAX(timestamp) FROM tableB b2 WHERE b2.box_id = A.box_id AND b2.timestamp <= A.timestamp) ORDER BY A.timestamp
id timestamp rainfall hail weather 373001645 2020-05-07 06:00:20 0.114 20.808 {"Hail": 20.808, "Rainfall": 0.114} 373001695 2020-05-07 06:02:26 0.12 15.544 {"Hail": 15.544, "Rainfall": 0.12} 373001762 2020-05-07 06:05:17 0.004 51.85 {"Hail": 51.85, "Rainfall": 0.004} 373001794 2020-05-07 06:06:38 0.02 5.8965 {"Hail": 5.8965, "Rainfall": 0.02} 373001810 2020-05-07 06:07:21 0.34 1.32 {"Hail": 1.32, "Rainfall": 0.34}