在SQL Server中，您可以将TABLESAMPLE与NEWID()结合使用，以获得相当好的随机性，并且仍然具有速度。如果您真的只想要1行或少量的行，这尤其有用。

SELECT TOP 1 * FROM [table] 
TABLESAMPLE (500 ROWS) 
ORDER BY NEWID()

用于MySQL获取随机记录

 SELECT name
  FROM random AS r1 JOIN
       (SELECT (RAND() *
                     (SELECT MAX(id)
                        FROM random)) AS id)
        AS r2
 WHERE r1.id >= r2.id
 ORDER BY r1.id ASC
 LIMIT 1

详情http://jan.kneschke.de/projects/mysql/order-by-rand/

ORDER BY NEWID()

耗时7.4毫秒

WHERE num_value >= RAND() * (SELECT MAX(num_value) FROM table)

只需要0.0065毫秒!

我肯定会选择后一种方法。

您也可以尝试使用new id()函数。

只需编写一个查询并使用order by new id()函数。它是随机的。

SQL Server

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。

 SELECT * FROM table ORDER BY RAND() LIMIT 1