SQL更新查询填充从第一行只有第一个值

Question

我有三个不同的表：人，person_pet和PET

create table person ( 
    id integer primary key, 
    name text 
); 

create table person_pet (
    person_id integer, 
    pet_id integer primary key 
); 

create table pet (
    id integer primary key, 
    breed text, 
    owner integer 
); 

在那之后，我插入一些值：

insert into person (id, name) 
    values (0, "Name1"), (1, "Name2"), (2, "Name3"); 

insert into person_pet (person_id, pet_id) 
    values (0,1), (1,0), (2,3), (1,2); 

insert into pet (id, breed, owner) 
    values (0, "PetA", null), (1, "PetB", null), (2, "PetC", null), (3, "PetD", null); 

我想将表pet中owner列的数据更新为person_pet表中显示的所有者的实际id。也就是说，我希望得到以下结果：

PET表

id breed owner 
0  PetA  1 
1  PetB  0 
2  PetC  1 
3  PetD  2 

我试图用一个选择的子查询这个SQL查询：

update pet set owner = (
    select person.id 
    from person, person_pet, pet 
    where person.id = person_pet.person_id and 
    person_pet.pet_id = pet.id 
); 

这产生这个输出（在只有ID填充一个所有者）：

PET表

id breed owner 
0  PetA  1 
1  PetB  1 
2  PetC  1 
3  PetD  1 

如果我运行它自己的子查询，

select person.id 
    from person, person_pet, pet 
    where person.id = person_pet.person_id and 
    person_pet.pet_id = pet.id; 

，我希望出现的结果：

PET表

id breed owner 
0  PetA  1 
1  PetB  0 
2  PetC  1 
3  PetD  2 

但我不使用时，设法让这更新命令。

Answer 1

我做这个测试的SQL Server解决方案， 可以帮助你：

update pet set owner = person.id 
from pet inner join person_pet on pet.id = person_pet.pet_id 
inner join person on person.id = person_pet.person_id 

与此输出：

id breed owner 
0 PetA 1 
1 PetB 0 
2 PetC 1 
3 PetD 2 

Answer 2

SQLite的，请尝试以下格式：

UPDATE pet 
SET owner = (
     SELECT PER.id 
     FROM person PER 
     INNER JOIN person_pet PPE ON PPE.person_id = PER.id 
     INNER JOIN pet PET ON PET.id = PPE.pet_id) 
WHERE id IN (SELECT id FROM pet);