mysql查询选择除某物以外的所有东西 [英] mysql query to select all except something

问题描述

我正试图选择只在餐桌上购买蔬菜的客户.但是我只能在查询中使用.我该怎么做?

i'm trying to select the customers who purchase only vegetables in food table.But i can't use except in query.How can i do this?

    create table Order (
        email varchar(30),
        nOrder integer,
        primary key (email, nOrder),
        foreign key (email) references Client(email)
    );

    create table RegisterOrder (
        email varchar(30),
        nOrder integer,
        nameA varchar(30),
        primary key (email,nOrder,nameA),
        foreign key (email,nOrder) references Order(email, nOrder),
        foreign key (nameA) references Dishe(nameA)
    );

create table Dishe(
    nameA varchar(30),
    primary key (nameA),
    foreign key (nameA) references Food(nameA));

    create table Food ( 
      nameA varchar(30), 
      type varchar(30),
      primary key (nameA)
    );

推荐答案

select ro.email
from registerorder ro 
inner join food f on f.namea = ro.namea
group by ro.email
having sum(f.type <> 'vegtables') = 0

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