SQLServer:

select top 10 * from tablename;

select top 10 percent from tablename;

select * from tablename limit 10;

SYBASE:

select top 10 * from tablename;

ORACLE:

oracle中无top命令，可使用以下语句查询前N行记录：

select * from table_name where rownum<=10;

top 命令SQLServer-sybase-oracle