Question

我运行此查询以使用随机数填充字段，但它会保留一些重复记录。知道如何删除重复项吗？

UPDATE APRFIL
SET ALTATH = CONVERT(int, RAND(CHECKSUM(NEWID())) * 10000);

Answer 1

生成的随机值可能已存在于表中。试试这个。

UPDATE APRFIL
SET    ALTATH = (SELECT ran
                 FROM   (SELECT CONVERT(INT, Rand(Checksum(Newid())) * 10000) ran) a
                 WHERE  NOT EXISTS (SELECT 1
                                    FROM   APRFIL Ap
                                    WHERE  ap.ALTATH = a.ran))

更新：最好删除重复的行并插入新记录。使用while循环插入所需数量的记录

Insert into APRFIL(ALTATH)
SELECT ran FROM   (SELECT CONVERT(INT, Rand(Checksum(Newid())) * 10000) ran) a
                     WHERE  NOT EXISTS (SELECT 1
                                        FROM   APRFIL Ap
                                        WHERE  ap.ALTATH = a.ran)

Answer 2

您可以使用随机数生成相关数字然后与行号上的原始表联接以选择随机数：

-- create temp table with numbers
    ;WITH r AS (
        SELECT 1 AS n
        UNION ALL
        SELECT n+1 FROM r WHERE n+1<=10000
    )
    SELECT n, ROW_NUMBER() OVER( ORDER BY NEWID()) random INTO #tempnums FROM r
    OPTION (Maxrecursion 0)

-- update 

    UPDATE x SET ALTATH=t.random
    FROM (SELECT *, ROW_NUMBER() OVER(ORDER BY ALTATH) rown FROM APRFIL) x 
    JOIN #tempnums t ON t.n=x.rown

从填充的字段中删除重复记录

2 个答案: