Oracle集合

--union  并集
select  * from emp where ename like '%A%' union
select * from emp where ename like '%M%';
--union all  集并  公共部分 会包含二次
 select * from emp where ename like '%A%' 
  union all 
  select * from emp where ename like '%M%'; 
 --intersert交集  
 select * from emp where ename like '%A%' 
     intersect 
     select * from emp where ename like '%M%'; 
 --minus求差集  S1: A -  (S1&S2 union)1100-1200
      select * from emp where sal between 700 and 1200   --700-1100;  
     minus
     select  * from emp where sal between  1100 and 1500;

--联合与全联合运算
 --union
 create table emp_history as select * from emp ;--辅助
 
 select empno,ename,sal,hiredate,deptno 
 from emp where deptno =20
 union
 select empno,ename,sal,hiredate,deptno 
 from emp_history where deptno =30
 order by deptno;
 
 -- union all 不能消除重复行,不能输出排序 使用DISTINCT关键字
  select empno,ename,sal,hiredate,deptno 
 from emp where deptno =20
 union  all
 select empno,ename,sal,hiredate,deptno 
 from emp_history where deptno =30
 order by deptno;
 
 --相交运算   1.列数和数据类型与select语句一样,但列名可以不同
 
 select empno,ename,sal,hiredate,deptno from emp
  where deptno =20 intersect
  select empno,ename,sal,hiredate,deptno from emp_history
  where deptno=20;
  
--相减运算
--查询在第一个表中而不再第二个表中的行
select empno,ename,sal,hiredate,deptno from emp
where deptno=20
minus
select empno,ename,sal,hiredate,deptno from emp
where deptno=20;  
--结构化查询   实现递归表的查询
select * from emp;
select level,lpad(' ',2*(level-1))||ename, empno,mgr,hiredate,sal  from emp
start with mgr is null  --start with以manager_id is null作为跟节点
connect by prior empno=mgr;  
--根据connect by prior规则,继续向下寻找,形成树状结构查询
 
--用子查询插入数据
create table emp_copy as select * from emp where 1=2;
insert into emp_copy select * from emp where deptno=20;
--insert插入多表数据
create table emp_dept_10 as select * from emp where 1=2;
create table emp_dept_20 as select * from emp where 1=2;
create table emp_dept_30 as select * from emp where 1=2;
insert first
  when deptno =10
    then 
      into emp_dept_10
    when deptno=20
      then 
        into emp_dept_20
      when deptno=30
      then
        into emp_dept_30
      else
         into emp_copy
       select * from emp;          
 
select * from emp_dept_10;
--Merge语句
merge into emp_copy c       --目标表
using emp e on (c.empno=e.empno)   --源表,可以是表,视图或查询
when MATCHED then update           --当匹配时,进行update操作
  set c.ename=e.ename,c.job=e.job,c.mgr=e.mgr,
      c.hiredate=e.hiredate,c.sal=e.sal,c.comm=e.comm,
      c.deptno =e.deptno
   when not matched then
      insert
      values(e.empno,e.ename,e.job,e.mgr,e.hiredate,e.sal,e.comm,
      e.deptno);
      

create table dept60_bonuses
( 
empno number,bonus_amt number
);
insert into dept60_bonuses values(7369,0);
insert into dept60_bonuses values(7788,2);
insert into dept60_bonuses values(7876,3);
select  empno,sal,ename from emp;
select * from dept60_bonuses;
--合并两张表,根据不同的语句删除,更新
merge into dept60_bonuses b
using ( select empno,sal,deptno from emp where deptno=20) e
on (b.empno=e.empno) 
when matched then
update set b.bonus_amt =e.sal*0.2
where b.bonus_amt=0
delete where (e.sal>2500)
when not matched then
insert (b.empno,b.bonus_amt)
values (e.empno,e.sal*0.1)
where (e.sal<4000);      
使用TRUNCATE清除表数据
与delete语句相比,使用truncate命令速度更快,原因  DTL
1不会激活表的删除触发器
2 属于数据定义语言,不会产生撤销信息
3 主外键关系无法清除表内容,必须禁用约束
不能使用PLSQL语句块 直接调用
--禁用约束
alter table dept disable constraint pk_dept cascade;
提交 commit; 回滚 rollback;
--sql>
create table jobs (adds varchar2(10),jname varchar2(20),sal number(10),comm number(10));
delete from jobs;
insert into jobs values('OFFICE','办公文员',3000,5000);
savepoint sp;
insert into jobs values('FINANCE','财务人员',4000,8000);
select * from jobs;
rollback to savepoint sp;
使用集合方法
--exits 方法   集合的坐标元素是否存在
declare
        type projectlist is varray (50) of varchar2(16);
        project_list projectlist:=projectlist('网站','ERP','CRM','CMS');
begin
  if project_list.exists(5)
    then
      dbms_output.put_line('元素存在,其值为:'||project_list(5));
      else
        dbms_output.put_line('元素不存在');
        end if;
  end;