随机读取数据sql语句MsSql/mySql

作者：袖梨 2022-06-29

SQL Server随机读取一个表中若干条记录：

示例：

代码如下	复制代码
select top 10 id,title from news order by newid()

优化之后

在MSSQL中用以下方法随机读取3W多条数据，只用了1-2秒。而在实际运用中，肯定是不会随机读取这么多数据的

MSSQL

代码如下

复制代码

select id from tablename where id >= (select floor(rand() * ((select max(id) from tablename) -

(select min(id) from tablename)) + (select min(id) from tablename))) order by id

mySql 随机读取数据

rand()函数

代码如下	复制代码
select * from users order by rand() LIMIT 1

这条语随机取一条记录还是不错的选择

代码如下

复制代码

SELECT * FROM users AS t1 JOIN (SELECT ROUND(RAND() * ((SELECT MAX(userId) FROM `users`)-(SELECT MIN

(userId) FROM users))+(SELECT MIN(userId) FROM users)) AS userId) AS t2 WHERE t1.userId >= t2.userId

ORDER BY t1.userId LIMIT 1

执行该sql语句，用时0.039s，效率太给力了

代码如下

复制代码

SELECT * FROM users WHERE userId >= ((SELECT MAX(userId) FROM users)-(SELECT MIN(userId) FROM users))

* RAND() + (SELECT MIN(userId) FROM users) LIMIT 1

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