Select Top在不同数据库中的使用用法：
1. Oracle数据库
SELECT * FROM TABLE1 WHERE ROWNUM<=N
2. Infomix数据库
SELECT FIRST N * FROM TABLE1
3. DB2数据库
SELECT * ROW_NUMBER() OVER(ORDER BY COL1 DESC) AS ROWNUM WHERE ROWNUM<=N
或者
SELECT COLUMN FROM TABLE FETCH FIRST N ROWS ONLY
4. SQL Server数据库
SELECT TOP N * FROM TABLE1
5. Sybase数据库
SET ROWCOUNT N
GO
SELECT * FROM TABLE1
6. MySQL数据库
SELECT * FROM TABLE1 LIMIT N
7. FoxPro数据库
SELECT * TOP N FROM TABLE ORDER BY COLUMN