不同数据库SQL语句的差别

1，系统时间

Oracle：SYSDATE

SQLSever：getdate()

Access:date()  或者 now()

2，查询前n条记录

Oracel: Select * From (Select……) where rownum<=10    ((Select……)是要真正查询的语句)

SQLServer:Select * From…………Top 10

MySql：Select * From tablename Limit 10

3, 随即抽取

MySql: FROM `table` AS t1 JOIN (SELECT ROUND(RAND() * ((SELECT MAX(id) FROM `table`)-(SELECT MIN(id) FROM `table`))+(SELECT MIN(id) FROM `table`)) AS id) AS t2 WHERE t1.id >= t2.id ORDER BY t1.id LIMIT 1;