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