选择随机和独特的项目 SQL答案

【问题标题】：pick random and unique items SQL选择随机和独特的项目 SQL
【发布时间】：2019-12-02 14:24:33
【问题描述】：

我们正在尝试使用 1-37 之间的随机（和 unqiue）值填充表。但是，以下查询不是唯一的。

truncate table [dbo].[webscrape]
declare @date date = '1990-01-01',
@endDate date = Getdate()

while @date<=@enddate
begin
insert into [dbo].[webscrape](date,value1,value2,value3,value4,value5)
SELECT @date date,convert(int,(RAND()*37-1+1)) value1,
convert(int,(RAND()*37-1+1)) value2,
convert(int,(RAND()*37-1+1)) value3,
convert(int,(RAND()*37-1+1)) value4,
convert(int,(RAND()*37-1+1)) value5

set @date = DATEADD(day,1,@date)
end

【问题讨论】：

Generate unique random numbers using SQL的可能重复

标签： sql sql-server random unique

【解决方案1】：

如果value1、value2、value3、value4、value5 必须是来自 [1..37] 的 5 个唯一随机值，那么下面的 insert 可能会起作用：

;with ThirtySeven as (
    SELECT 1 As RowNum
    UNION ALL
    SELECT RowNum+1
        FROM ThirtySeven
        WHERE RowNum<37
), Randoms37 AS (
    SELECT 
        ROW_NUMBER() OVER (ORDER BY [RowNum]) as RowNum,
        ROW_NUMBER() OVER (ORDER BY NEWID()) as Random
    FROM ThirtySeven
)
insert into [dbo].[webscrape](date,value1,value2,value3,value4,value5)
SELECT @date date, [1], [2], [3], [4], [5] 
from (select Random, RowNum from randoms37 where RowNum<=5) rnd37 
    pivot (min(random) FOR RowNum in ([1], [2], [3], [4], [5])) as rnd37

【讨论】：

【解决方案2】：

主要点是具有可用值的创建表，并采用拾取的值 - 选择值，从可用中删除并添加到拣选。

declare @initData table (ID int)
declare @pickedData table (ID int)
declare @i  int =0;
declare @pickAmount int = 7;
declare @pickedIndex int = 0;
declare @pickedValue int = 0;
set @i = 0;
while @i<37
begin
set @i = @i+1;
insert into @initData VALUES (@i)
end
while (select count(ID) from @pickedData) < @pickAmount
begin
 set @pickedIndex = convert(int,(RAND()*(select count(ID)-1 from @initData)))
 select @pickedValue=id from @initData order by id  OFFSET (@pickedIndex) ROWS FETCH NEXT (1) ROWS ONLY 
 insert into @pickedData VALUES (@pickedValue)
 delete from @initData where id = @pickedValue;
end
select * from @pickedData;

【讨论】：