access：
select top (10) * from table1 where
1=1
db2：
select column from table where 1=1 fetch
first 10 rows only
mysql：
select * from table1 where 1=1 limit
10
sql server:
读取前10条：select top (10) * from table1 where
1=1
读取后10条：select top (10) * from table1 order
by id desc
oracle：
select * from table1 where rownum<=10