oracle取差值集合

Oracle Minus关键字
SQL中的MINUS关键字
SQL中有一个MINUS关键字,它运用在两个SQL语句上,它先找出第一条SQL语句所产生的结果,然后看这些结果有没有在第二个SQL语句的结果中。如果有的话,那这一笔记录就被去除,而不会在最后的结果中出现。如果第二个SQL语句所产生的结果并没有存在于第一个SQL语句所产生的结果内,那这笔资料就被抛弃,其语法如下:
[SQL Segment 1]
MINUS
[SQL Segment 2]
--------------------------------------------
//创建表1

create table test1

(

name varchar(10),

sex varchar(10),

);



insert into test1 values('test','female');

insert into test1 values('test1','female');

insert into test1 values('test1','female');

insert into test1 values('test11','female');

insert into test1 values('test111','female');


//创建表2

create table test2

(

name varchar(10),

sex varchar(10),

);

insert into test1 values('test','female');

insert into test1 values('test2','female');

insert into test1 values('test2','female');

insert into test1 values('test22','female');

insert into test1 values('test222','female');

-------------------------------------------

select * from test1 minus select * from test2;



结果:



NAME SEX 

---------- ---------- 

test1 female 

test11 female 

test111 female 

-----------------------------------------------------------



select * from test2 minus select * from test1;



结果:



NAME SEX 

---------- ---------- 

test2 female 

test22 female 

test222 female

结论:Minus返回的总是左边表中的数据,它返回的是差集。注意:minus有剃重作用

==========================================================
下面是我做的实验,很明显能够看出MINUS的效率,made_order共23万笔记录,charge_detail共17万笔记录

性能比较:

SELECT order_id FROM made_order

  MINUS

  SELECT order_id FROM charge_detail

  1.14 sec

  SELECT a.order_id FROM made_order a

  WHERE NOT exists (

   SELECT order_id

   FROM charge_detail

   WHERE order_id = a.order_id

   )

  18.19 sec

  SELECT order_id FROM made_order

  WHERE order_id NOT in (

   SELECT order_id

   FROM charge_detail

   )

  20.05 sec

还有其它一下关键字:
INTERSECT (交集)
UNION ALL 并集

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