db2, oracle和sqlserver取前几行的语法

   db2：
       select * from tab fetch first 10 rows only
  oracle:
      select * from tab where rownum <=10
  sqlserver:
      select top 10 * from tab
  mysql:
      select * from tab limit 10

   db2：
       select * from tab fetch first 10 rows only
  oracle:
      select * from tab where rownum <=10
  sqlserver:
      select top 10 * from tab
  mysql:
      select * from tab limit 10