Oracle minus使用

新建两个表：

create table guotest1
(
       sName varchar2(10),
       Gender varchar2(10)
)

create table guotest2
(
       sName varchar2(10),
       Gender varchar2(10)
)

插入数据：

insert into guotest1 values('a', 'm');
insert into guotest1 values('b', 'm');
insert into guotest1 values('c', 'f');
insert into guotest1 values('d', 'f');

insert into guotest2 values('e', 'm');
insert into guotest2 values('f', 'm');
insert into guotest2 values('g', 'f');
insert into guotest2 values('h', 'f');

1 minus返回的是两个查询结果表的差集

例如：select * from guotest1 where rownum <= 4 minus select * from guotest1 where rownum <= 2

返回结果：

"SNAME","GENDER"
"c","f"
"d","f"

2 minus返回的记录总是来自于左边的表

例如：select * from guotest1 minus select * from guotest2

返回结果：

"SNAME","GENDER"
"a","m"
"b","m"
"c","f"
"d","f"

像是说：如果左边的表中的某个记录存在于右边的表中，则该记录不会返回