新建兩個表：

create table guotest1

(

sName varchar2(10),

Gender varchar2(10)

)

create table guotest2

(

sName varchar2(10),

Gender varchar2(10)

)

插入數據：

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返回的是兩個查詢結果表的差集

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

返回結果：

"SNAME","GENDER"

"c","f"

"d","f"

2 minus返回的記錄總是來自于左邊的表

例如：select * from guotest1 minus select * from guotest2

返回結果：

"SNAME","GENDER"

"a","m"

"b","m"

"c","f"

"d","f"

像是說：如果左邊的表中的某個記錄存在于右邊的表中，則該記錄不會返回

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