Oracle数据库的查询

--去除重复记录

select distinct  ssex from java1227;
select distinct  (ssex) from java1227;

--给指定字段指定别名
select ssid as 编号 ,sname as 姓名 from java

--排序 倒序 desc
select * from java1227 order by ssid desc;

--模糊查询
select * from java0322 where sname like ‘___‘;
select * from java0322 where sname like ‘%四%‘;

--内连接
select * from java0322 join sclass on java0322.cid =sclass.cid;
-- 给表起别名
select * from java0322 a join sclass b on a.cid = b.cid;

--左外连接(左边的全部）
select * from sclass  a left join java0322 b on a.cid =b.cid;

--右外连接（右表的全部）
select * from java0322 a right join sclass b on a.cid =b.cid;

--全外连接

select * from sclass a full join java0322 b on a.cid = b.cid;

-- 查询男女各多少(按性别分组后查询所有，然后再查个数）
select ssex,count(*) from java1227 group by ssex;

-- 查询性别大于1 的性别
select ssex from java1227 group by ssex having count(*)>1;

-- 子查询--查询性别为女的学生所在的班级
select cname from sclass where cid in (select cid from java0322 where ssex=‘女‘);
--查询阳光班的所有男同学的地址
select saddress from java0322 where ssex =‘男‘and cid in(select cid from sclass where cname=‘阳光班‘);

select saddress from java0322 a join sclass b on a.cid = b.cid where ssex=‘男‘ and cname=‘阳光班‘;

select * from (select sclass.cid,cname,ssid,sname from sclass join java0322 on java0322.cid = sclass.cid)

--分行---查询第2条
select * from(select rownum as num,sclass.cid,cname,ssid,sname from sclass join java0322 on java0322.cid = sclass.cid) where num >1 and num<3;