Newid ()/order by可以工作，但对于大型结果集来说代价非常高，因为它必须为每一行生成一个id，然后对它们进行排序。

从性能的角度来看，TABLESAMPLE()很好，但是您将得到结果的聚集(将返回页面上的所有行)。

为了获得更好的真实随机样本，最好的方法是随机过滤掉行。我在SQL Server Books Online文章使用TABLESAMPLE限制结果集中找到了以下代码示例:

If you really want a random sample of individual rows, modify your query to filter out rows randomly, instead of using TABLESAMPLE. For example, the following query uses the NEWID function to return approximately one percent of the rows of the Sales.SalesOrderDetail table: SELECT * FROM Sales.SalesOrderDetail WHERE 0.01 >= CAST(CHECKSUM(NEWID(),SalesOrderID) & 0x7fffffff AS float) / CAST (0x7fffffff AS int) The SalesOrderID column is included in the CHECKSUM expression so that NEWID() evaluates once per row to achieve sampling on a per-row basis. The expression CAST(CHECKSUM(NEWID(), SalesOrderID) & 0x7fffffff AS float / CAST (0x7fffffff AS int) evaluates to a random float value between 0 and 1.

当对一个有1,000,000行的表运行时，下面是我的结果:

SET STATISTICS TIME ON
SET STATISTICS IO ON

/* newid()
   rows returned: 10000
   logical reads: 3359
   CPU time: 3312 ms
   elapsed time = 3359 ms
*/
SELECT TOP 1 PERCENT Number
FROM Numbers
ORDER BY newid()

/* TABLESAMPLE
   rows returned: 9269 (varies)
   logical reads: 32
   CPU time: 0 ms
   elapsed time: 5 ms
*/
SELECT Number
FROM Numbers
TABLESAMPLE (1 PERCENT)

/* Filter
   rows returned: 9994 (varies)
   logical reads: 3359
   CPU time: 641 ms
   elapsed time: 627 ms
*/    
SELECT Number
FROM Numbers
WHERE 0.01 >= CAST(CHECKSUM(NEWID(), Number) & 0x7fffffff AS float) 
              / CAST (0x7fffffff AS int)

SET STATISTICS IO OFF
SET STATISTICS TIME OFF

如果您可以使用TABLESAMPLE，它将为您提供最佳性能。否则使用newwid ()/filter方法。如果结果集很大，Newid ()/order by应该是最后的选择。

我在子查询中使用它，它在子查询中返回我相同的行

 SELECT  ID ,
            ( SELECT TOP 1
                        ImageURL
              FROM      SubTable 
              ORDER BY  NEWID()
            ) AS ImageURL,
            GETUTCDATE() ,
            1
    FROM    Mytable

然后我解决了包括父表变量在哪里

SELECT  ID ,
            ( SELECT TOP 1
                        ImageURL
              FROM      SubTable 
              Where Mytable.ID>0
              ORDER BY  NEWID()
            ) AS ImageURL,
            GETUTCDATE() ,
            1
    FROM    Mytable

注意where条件

select  * from table
where id in (
    select id from table
order by random()
limit ((select count(*) from table)*55/100))

// to select 55 percent of rows randomly

select top 10 percent * from [yourtable] order by newid()

针对关于大型表的“纯粹垃圾”评论:您可以这样做以提高性能。

select  * from [yourtable] where [yourPk] in 
(select top 10 percent [yourPk] from [yourtable] order by newid())

这样做的成本将是值的关键扫描加上连接成本，对于一个选择百分比较小的大表来说，这应该是合理的。

如果你知道你有大约N行，你想要大约K个随机行，你只需要以K/N的概率拉任意给定的行。使用RAND()函数，它给你一个在0和1之间的公平分布，你可以只做下面的事情，其中PROB = K/N。对我来说效果很快。

SELECT * FROM some_table WHERE RAND() < PROB

在MySQL中，你可以这样做:

SELECT `PRIMARY_KEY`, rand() FROM table ORDER BY rand() LIMIT 5000;