sql - SQL where x 或 y 但不是两者

Question

我有一张桌子，列出了供应牛肉鸡肉的餐厅，与此类似：

Res   Meat
res1  chicken
res1  chicken
res1  beef
res2  chicken
res2  chicken
res3  beef

我正在尝试编写一个查询，返回哪些餐厅只提供鸡肉或牛肉，而不是两者都提供，而不消除结果中的重复项。

Answer 1

试试这个：

CREATE TABLE rest 
    (
     id int auto_increment primary key, 
     Res varchar(20),
     Meat varchar(20) 
    );

INSERT INTO rest
(Res,Meat)
VALUES
('res1','chicken'),
('res1', 'chicken'),
('res1', 'beef'),
("res2", 'chicken'),
("res2", 'chicken'),
( 'res3', 'beef' )

select Res from 
  (select distinct Res,Meat from rest ) test
group by Res
having count(1) = 1

SQLFiddle 上的示例，

Answer 2

试试这个方法：

create table tab
(
   Res   varchar(10), 
   Meat varchar(10)
)

insert into tab ( Res, Meat ) values ( 'res1', 'chicken' )
insert into tab ( Res, Meat ) values ( 'res1', 'chicken' )
insert into tab ( Res, Meat ) values ( 'res1', 'beef' )    
insert into tab ( Res, Meat ) values ( 'res2', 'chicken' )
insert into tab ( Res, Meat ) values ( 'res2', 'chicken' )    
insert into tab ( Res, Meat ) values ( 'res3', 'beef' )

select Res
from (
select distinct Res,Meat
from tab ) T
group by Res
having count(1) = 1

Answer 3

您可以使用 except 运算符

select * from table
where meat = 'chicken' or meat = 'Beer'

except

select * from table
where meat = 'chicken' and meat = 'Beer'

Answer 4

尝试：

select Res 
from rest
group by Res
having count(distinct Meat) = 1