一道要求按比例更新数据问题的解答

QA要求帮忙将样例表中的数据按比例更新：

例如,要求按如下规则更新某列

50%的数据，更新为A
25%的数据，更新为B
20%的数据，更新为C
5%的数据，  更新为D
 
解决方案如下:
 
---示例数据表
DECLARE @PercentSetting TABLE
      (Id INT IDENTITY PRIMARY KEY,
       A INT,
       Percentage NVARCHAR(50)
      )
 
 
--循环插入1000条数据
DECLARE @I INT
SET @I=1
 
WHILE @I <= 1000
BEGIN
 
 INSERT INTO @PercentSetting(A)
 SELECT @I*100
 SET @I=@I+1
END
 
--按比例更新-------------------
DECLARE @TempTable TABLE
(Id INT IDENTITY PRIMARY KEY,
 KeyCol1 INT,
 keyCol2 INT--可能需要多列主键字段
 )
 
 
INSERT INTO @TempTable(KeyCol1)
SELECT
      Id
FROM @PercentSetting
WHERE Percentage is null
ORDER BY NEWID()--随机排序
 
--先设置50%
UPDATE t
SET t.Percentage='A'
FROM @PercentSetting AS t
      INNER JOIN @TempTable AS tt ON t.Id = tt.KeyCol1
WHERE tt.Id % 2 = 0
 
DELETE @TempTable
 
INSERT INTO @TempTable(KeyCol1)
SELECT
      Id
FROM @PercentSetting
WHERE Percentage IS NULL
ORDER BY NEWID()--随机排序
 
--剩余50%的50%即为25%
UPDATE t
SET Percentage='B'
FROM @PercentSetting AS t
      inner join @TempTable AS tt ON t.Id = tt.KeyCol1
WHERE tt.Id % 2 = 0
 
DELETE @TempTable
 
INSERT INTO @TempTable(KeyCol1)
SELECT
      Id
FROM @PercentSetting
WHERE Percentage IS NULL
ORDER BY NEWID()--随机排序
 
--再剩余(25%)的1/5即为总数的5%
UPDATE t
SET Percentage = 'D'
FROM @PercentSetting AS t
      INNER JOIN @TempTable AS tt ON t.Id = tt.KeyCol1
WHERE tt.Id % 5 = 0
 
--剩余的即为20%
UPDATE @PercentSetting
SET Percentage='C'
WHERE Percentage IS NULL
 
 
--验证结果
--验证结果
SELECT
      Percentage,
      COUNT(*) CountOf1000
FROM @PercentSetting
GROUP BY Percentage
 
 
Percentage                                         CountOf1000
-------------------------------------------------- -----------
A                                                  500
B                                                  250
C                                                  200
D                                                  50