Oracle的一些基本语句

oracle创建联合主键:

alter table R$ZZLD_R$HLWJG add constraint pk_R$ZZLD_R$HLWJG primary key (HLW_USERNAME,HLW_PHONE,HLW_ORGCODE);

oracle随机获取N条数据

select * from (select * from tablename order by dbms_random.value) where rownum< N;