1 --union  并集  2 select  * from emp where ename like '%A%' union  3 select * from emp where ename like '%M%';  4 --union all  集并  公共部分 会包含二次  5  select * from emp where ename like '%A%'   6   union all   7   select * from emp where ename like '%M%';   8  --intersert交集    9  select * from emp where ename like '%A%'  10      intersect  11      select * from emp where ename like '%M%';  12  --minus求差集  S1: A -  (S1&S2 union)1100-1200 13       select * from emp where sal between 700 and 1200   --700-1100;   14      minus 15      select  * from emp where sal between  1100 and 1500; 16  17 --联合与全联合运算 18  --union 19  create table emp_history as select * from emp ;--辅助 20   21  select empno,ename,sal,hiredate,deptno  22  from emp where deptno =20 23  union 24  select empno,ename,sal,hiredate,deptno  25  from emp_history where deptno =30 26  order by deptno; 27   28  -- union all 不能消除重复行,不能输出排序 使用DISTINCT关键字 29   select empno,ename,sal,hiredate,deptno  30  from emp where deptno =20 31  union  all 32  select empno,ename,sal,hiredate,deptno  33  from emp_history where deptno =30 34  order by deptno; 35   36  --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 37   38  select empno,ename,sal,hiredate,deptno from emp 39   where deptno =20 intersect 40   select empno,ename,sal,hiredate,deptno from emp_history 41   where deptno=20; 42    43 --相减运算 44 --查询在第一个表中而不再第二个表中的行 45 select empno,ename,sal,hiredate,deptno from emp 46 where deptno=20 47 minus 48 select empno,ename,sal,hiredate,deptno from emp 49 where deptno=20;   50 --结构化查询   实现递归表的查询 51 select * from emp; 52 select level,lpad(' ',2*(level-1))||ename, empno,mgr,hiredate,sal  from emp 53 start with mgr is null  --start with以manager_id is null作为跟节点 54 connect by prior empno=mgr;   55 --根据connect by prior规则,继续向下寻找,形成树状结构查询 56   57 --用子查询插入数据 58 create table emp_copy as select * from emp where 1=2; 59 insert into emp_copy select * from emp where deptno=20; 60 --insert插入多表数据 61 create table emp_dept_10 as select * from emp where 1=2; 62 create table emp_dept_20 as select * from emp where 1=2; 63 create table emp_dept_30 as select * from emp where 1=2; 64 insert first 65   when deptno =10 66     then  67       into emp_dept_10 68     when deptno=20 69       then  70         into emp_dept_20 71       when deptno=30 72       then 73         into emp_dept_30 74       else 75          into emp_copy 76        select * from emp;           77   78 select * from emp_dept_10; 79 --Merge语句 80 merge into emp_copy c       --目标表 81 using emp e on (c.empno=e.empno)   --源表,可以是表,视图或查询 82 when MATCHED then update           --当匹配时,进行update操作 83   set c.ename=e.ename,c.job=e.job,c.mgr=e.mgr, 84       c.hiredate=e.hiredate,c.sal=e.sal,c.comm=e.comm, 85       c.deptno =e.deptno 86    when not matched then 87       insert 88       values(e.empno,e.ename,e.job,e.mgr,e.hiredate,e.sal,e.comm, 89       e.deptno); 90        91  92 create table dept60_bonuses 93 (  94 empno number,bonus_amt number 95 ); 96 insert into dept60_bonuses values(7369,0); 97 insert into dept60_bonuses values(7788,2); 98 insert into dept60_bonuses values(7876,3); 99 select  empno,sal,ename from emp;100 select * from dept60_bonuses;101 --合并两张表,根据不同的语句删除,更新102 merge into dept60_bonuses b103 using ( select empno,sal,deptno from emp where deptno=20) e104 on (b.empno=e.empno) 105 when matched then106 update set b.bonus_amt =e.sal*0.2107 where b.bonus_amt=0108 delete where (e.sal>2500)109 when not matched then110 insert (b.empno,b.bonus_amt)111 values (e.empno,e.sal*0.1)112 where (e.sal<4000);      113 使用TRUNCATE清除表数据114 与delete语句相比,使用truncate命令速度更快,原因  DTL115 1不会激活表的删除触发器116 2 属于数据定义语言,不会产生撤销信息117 3 主外键关系无法清除表内容,必须禁用约束118 不能使用PLSQL语句块 直接调用119 --禁用约束120 alter table dept disable constraint pk_dept cascade;121 提交 commit; 回滚 rollback;122 --sql>123 create table jobs (adds varchar2(10),jname varchar2(20),sal number(10),comm number(10));124 delete from jobs;125 insert into jobs values('OFFICE','办公文员',3000,5000);126 savepoint sp;127 insert into jobs values('FINANCE','财务人员',4000,8000);128 select * from jobs;129 rollback to savepoint sp;130 使用集合方法131 --exits 方法   集合的坐标元素是否存在132 declare133         type projectlist is varray (50) of varchar2(16);134         project_list projectlist:=projectlist('网站','ERP','CRM','CMS');135 begin136   if project_list.exists(5)137     then138       dbms_output.put_line('元素存在,其值为:'||project_list(5));139       else140         dbms_output.put_line('元素不存在');141         end if;142   end;