重复密钥更新不会更新而是插入一行

Question

INSERT INTO min_product ( shopid, productid , outward ) 
SELECT shopid, productid , outward 
FROM main_product 
WHERE shopid= '51' 
    ON DUPLICATE KEY UPDATE outward  = ( SELECT sum(outward)  
                                         FROM main_product WHERE shopid= '51' )

main_product表

productid outward shopid
    333      2      44//present
    343      4      44//present
    353      5      44//present
    363      1      44//present
    373      2      44//not present

min_product表

productid outward shopid

333      1      44
343      1      44
353      1      44
363      1      44

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问题是它没有在重复行上更新而是插入了新行？查询ON DUPLICATE KEY UPDATE

中的问题是什么

Answer 1

如果您的数据库允许插入重复行，则表的定义不正确 - 仅在插入UNIQUE索引或PRIMARY KEY的副本时才执行更新

INSERT ... ON DUPLICATE KEY UPDATE Syntax