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MySQL update时使用联表，聚合

2024-08-24 11:00:32   217人阅读

原文地址 http://stackoverflow.com/questions/3022405/mysql-update-query-with-left-join-and-group-by

 

UPDATE
    Table AS t
    LEFT JOIN (
        SELECT
            Index1,
            Index2,
            COUNT(EventType) AS NumEvents
        FROM
            MEvents
        WHERE
            EventType = ‘A‘ OR EventType = ‘B‘
        GROUP BY
            Index1,
            Index2
    ) AS m ON
        m.Index1 = t.Index1 AND
        m.Index2 = t.Index2
SET
    t.SpecialEventCount = m.NumEvents
WHERE
    t.SpecialEventCount IS NULL

 

MySQL update时使用联表，聚合


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