Question

我的Android应用程序中有三个表。

Table Animal   Table Group   TableGroup_Animal
idAnimal       idGroup       idAnimal
AnimalName     groupName     idGroup

我想知道如何进行查询以获取组内的所有动物。我提出的查询是

select
    Groups.groupName
from
    Groups,
    Animal,
    tableGrupo_Animal
where
    Animal.idanimal = tableGroup_Animal.fkanimal
    and
    Groups.idgrupo = tableGrupo_Animal.fkgrupo
group by
    group.groupName

此外（仅显示第一行）

select
    *
from
    Animal
    INNER JOIN " + tableGroup + " ON Animal.idanimal = Group.idGroup
where
    Group.groupName = ' " + groupName +

正如我所说，我希望将所有动物都集中在一个群体中，我该怎么做？感谢

Answer 1

我在sqlite中重新创建了数据库并对其进行了测试。这个SQL工作得很好。我建议你重命名你的桌子＆＃34; Group＆＃34;因为它是SQL中的保留字，你必须每次都像我在这个sql中那样回复它。

select a.AnimalName, g.groupName 
    from Animal a 
        JOIN TableGroup_Animal tga ON a.idAnimal = tga.idAnimal
        JOIN `Group` g on g.idGroup= tga.idGroup;

这是我创建的架构和数据，以帮助任何人尝试原型。

    CREATE TABLE `Animal` (
    `idAnimal`  INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE,
    `animalName`    varchar(128)
);

CREATE TABLE `Group` (
    `idGroup`   INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE,
    `groupName` varchar(128)
);

CREATE TABLE `TableGroup_Animal` (
    `id`    INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE,
    `idAnimal`  integer,
    `idGroup`   integer
);

--Seeding animal
insert into `Animal` (animalName) values ('cat');
insert into `Animal` (animalName) values ('Rat');
insert into `Animal` (animalName) values ('Zebra');
insert into `Animal` (animalName) values ('Platypus');

--seeding group
insert into `Group` (groupName) values ('small');
insert into `Group` (groupName) values ('medium');
insert into `Group` (groupName) values ('large');

---seeding group animal pivot table
insert into TableGroup_Animal (idAnimal, idGroup) values (3,2);
insert into TableGroup_Animal (idAnimal, idGroup) values (3,3);
insert into TableGroup_Animal (idAnimal, idGroup) values (1,2);
insert into TableGroup_Animal (idAnimal, idGroup) values (4,2);
insert into TableGroup_Animal (idAnimal, idGroup) values (2,1);
);
insert into TableGroup_Animal (idAnimal, idGroup) values (2,1);

Answer 2

执行此查询：

 select * from Animal INNER JOIN tableGrupo_Animal ON Animal.idanimal = tableGrupo_Animal.fkanimal INNER JOIN Grupos ON Grupos.idgrupo = tableGrupo_Animal.fkgrupo where Grupos.nomegrupo='wwrt'

如何用2个外键查询表？

2 个答案: