使用 NEWID() 使用随机数据更新表不起作用

Question

SQL 服务器 2000：

我有一个包含测试数据的表（大约 100000 行），我想用另一个表中的一些随机数据更新另一个表中的列值。根据this question，这就是我正在尝试的：

UPDATE testdata
SET type = (SELECT TOP 1 id FROM testtypes ORDER BY CHECKSUM(NEWID()))

-- or even
UPDATE testdata
SET type = (SELECT TOP 1 id FROM testtypes ORDER BY NEWID())

但是，“类型”字段对于所有行仍然具有相同的值；任何想法我做错了什么？

[编辑] 我希望这个查询为每一行返回一个不同的值，但它不会：

SELECT testdata.id, (SELECT TOP 1 id FROM testtypes ORDER BY CHECKSUM(NEWID())) type
FROM testdata

-- however seeding a rand value works
SELECT testdata.id, (SELECT TOP 1 id FROM testtypes ORDER BY CHECKSUM(NEWID()) + RAND(testdata.id)) type
FROM testdata

Answer 1

您的问题是：您只选择了一个单个值，然后使用该单个值更新所有列。

为了真正实现随机化，您需要逐步/循环方法 - 我在 SQL Server 2008 中尝试过，但我认为它也应该在 SQL Server 2000 中工作：

-- declare a temporary TABLE variable in memory
DECLARE @Temporary TABLE (ID INT)

-- insert all your ID values (the PK) into that temporary table
INSERT INTO @Temporary SELECT ID FROM dbo.TestData

-- check to see we have the values
SELECT COUNT(*) AS 'Before the loop' FROM @Temporary 

-- pick an ID from the temporary table at random    
DECLARE @WorkID INT
SELECT TOP 1 @WorkID = ID FROM @Temporary ORDER BY NEWID()

WHILE @WorkID IS NOT NULL
BEGIN
    -- now update exactly one row in your base table with a new random value
    UPDATE dbo.TestData
    SET [type] = (SELECT TOP 1 id FROM dbo.TestTypes ORDER BY NEWID())
    WHERE ID = @WorkID

    -- remove that ID from the temporary table - has been updated 
    DELETE FROM @Temporary WHERE ID = @WorkID

    -- first set @WorkID back to NULL and then pick a new ID from 
    -- the temporary table at random        
    SET @WorkID = NULL
    SELECT TOP 1 @WorkID = ID FROM @Temporary ORDER BY NEWID()
END

-- check to see we have no more IDs left
SELECT COUNT(*) AS 'After the update loop' FROM @Temporary 

Answer 2

您需要在选择新 ID 时强制执行每行计算 ..

这样就可以了

UPDATE testdata
SET type = (SELECT TOP 1 id FROM testtypes ORDER BY outerTT*CHECKSUM(NEWID()))
FROM testtypes outerTT