随机获取10条记录

mysql:    select * from tablename order by rand() limit 10 
sqlserver:    select top 10 * from tablename order by NEWID()

Sqlite：Select * From tablename order by random(*) limit 10

Oracle：

SELECT column FROM 
( SELECT column FROM table 
ORDER BY dbms_random.value ) 
WHERE rownum <= 10

PostgreSQL：

SELECT column FROM table 
ORDER BY RANDOM() 
LIMIT 10