189 8069 5689
Oracle 高级查询
1 集合运算
union 并集 把两张表合成一张表
intersect 交集 一样的留下，不一样的不要
minus 减去 前面的结果减去后面的结果
create table emp3 as select * from emp2 where deptno=20; create table emp4 as select * from emp2 where deptno=30; alter table emp3 rename to emp20; alter table emp4 rename to emp30; select * from emp20; select * from emp30; select * from emp20 union select * from emp30; select * from emp30 intersect select * from emp2; select * from emp2 minus select * from emp30;2 connect by 和start with
依托于该语法，我们可以将一个表形结构的以树的顺序列出来
提供一个伪列 level
level
找到头 select ename from emp2 where mgr is null; select empno,ename,mgr from emp start with ename='KING' connect by prior empno=mgr; select level,empno,ename,mgr from emp start with ename=(select ename from emp2 where mgr is null) connect by prior empno=mgr; select * from (select level lv,empno,ename,mgr from emp start with ename=(select ename from emp2 where mgr is null) connect by prior empno=mgr) where lv=2;3高级分组函数
rollup 函数 小计
rollup 函数多一行 小计
对于分组的列为null
对于聚集函数为求 小计
select job,sum(sal) from emp GROUP BY rollup(job); select job,sum(sal),round(avg(sal)),max(sal),count(empno)from emp group by rollup(job);统计rollup(x,y) 统计第一个x 不统计y
select dname,job,sum(sal) from emp inner join dept using(deptno) group by rollup(dname,job);cube 统计所有的列
select dname,job,sum(sal) from emp inner join dept using(deptno) froup by cube(dname,job) order by dname;rollup 和cube 就是汇总的结果
grouping 和grouping sets
select grouping(dname),dname ,grouping(job),job,sum(sal) from emp inner join dept using(deptno) group by rollup(dname,job) order by dname;select * from (select grouping(dname),dname ,grouping(job) N,job,sum(sal) from emp inner join dept using(deptno) group by rollup(dname,job) order by dname) where dname='SALES' and N=1 ;select grouping(dname),dname,grouping(job),job,sum(sal) from emp inner join dept using(deptno) group by cube(dname,job) order by dname;只查询汇总的行 总的汇总也不要
select dname,job,sum(sal) from emp inner join dept using(deptno) group by grouping sets(dname,job);如果需要查询的结果只有小计 可以用cube 和 grouping sets 用grouping sets 的效率高于cube 和rollup
排名函数
既能排序又能排名
rank() over( orader by xx)
重复就会削去下一个编号
select rank() over(order by sal desc),ename,sal from emp;dense_rank() over(orader by xx)
重复不削去编号
select dense_rank() over(order by sal desc),ename,sal from emp;先排序在rownum 比rownum 简单
select row_number() over(order by sal desc),ename from emp;另外有需要云服务器可以了解下创新互联cdcxhl.cn，海内外云服务器15元起步，三天无理由+7*72小时售后在线，公司持有idc许可证，提供“云服务器、裸金属服务器、高防服务器、香港服务器、美国服务器、虚拟主机、免备案服务器”等云主机租用服务以及企业上云的综合解决方案，具有“安全稳定、简单易用、服务可用性高、性价比高”等特点与优势，专为企业上云打造定制，能够满足用户丰富、多元化的应用场景需求。