SQL where x 或 y 但不是两者

Question

我有一张 table ，上面列出了供应鸡肉或牛肉的餐厅，与此类似:

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

并且我正在尝试编写一个查询，该查询返回哪些餐厅只提供鸡肉或牛肉，但不能同时提供，而不会从结果中消除重复项。

Answer 1

尝试这个:

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

Example on SQLFiddle ,