本來要刪除error_barcode表中barcode值重復的只保留一條

表結構如下(PS:id是自增長，該圖是刪除成功所以id不連續)

sql語句如下：

DELETE
FROM
    error_barcode
WHERE
    barCode IN (
        SELECT
            barCode
        FROM
            error_barcode
        GROUP BY
            barCode
        HAVING
            count(barCode) > 1
    )
AND
 
 id NOT IN (

    SELECT
        min(id)
    FROM
        error_barcode
    GROUP BY
        barCode
    HAVING
        count(barCode) > 1
)

但是卻報錯誤

上網查找了下，這是MySql的一個問題，就是不能再同一個語句裏對同一張表先select某些值在update，

那就需要把子查詢在放入一個子查詢中

DELETE from error_barcode 
WHERE barCode in(
    select a.barCode from(select
 
 * from error_barcode)a  GROUP BY barCode having count(barCode)>1
)and id not in (
    select min(id) from(select * from error_barcode)b  GROUP BY barCode having count(barCode)>1
)

可以看到我把下面兩個子查詢

 SELECT
            barCode
        FROM
            error_barcode
        GROUP BY
            barCode
        
 
HAVING
            count(barCode) > 1

 SELECT
        min(id)
    FROM
        error_barcode
    GROUP BY
        barCode
    HAVING
        count(barCode) > 1

改成

select a.barCode from(select * from error_barcode)a  GROUP BY barCode having count(barCode)>1

 select min(id) from(select * from error_barcode)b  GROUP BY barCode having count(barCode)>1

就行了

MySql刪除重復只保留一條