mins

create table test1 (   name varchar(10),  sex varchar(10),  age int );
insert into test1 values('luxin','female',25); insert into test1 values('tom','female',26); insert into test1 values('mary1','male',27); insert into test1 values('money','male',27); insert into test1 values('tony','male',28); insert into test1 values('tony1','male',19);
create table test2 (   name varchar(10),  sex varchar(10),  age int );   
insert into test2 values('luxin','female',25); insert into test2 values('tom','female',26); insert into test2 values('mary2','male',27); insert into test2 values('money','male',27); insert into test2 values('tony','male',28); insert into test2 values('tony2','male',19);   

select * from test1 minus select * from test2;

结果： 
NAME       SEX          AGE
mary1      male         27
tony1      male         19  

select * from test2 minus select * from test1;

结果: 
NAME       SEX               AGE
mary2      male               27
tony2      male               19   

结论：Minus返回的总是左边表中的数据，它返回的是差集。
用表1-表2中的数据，如果相同，则去掉，否则返回表1中的数据。