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;