將兩行合併爲一個

Question

下面的查詢爲我提供了兩行，因爲該學生有兩個聯繫人。我希望能夠做到的是在一行中顯示兩個聯繫人。

如果有人能夠幫助我，我會非常感激。

查詢

select student.code as "student code", student.firstname, student.surname, student.birth_date, contact.firstname as "contact firtname", contact.surname as "contact surname" 
from 
student 
join "studentContact" on student.id = "studentContact".student 
join contact on "studentContact".contact = contact.id 

輸出

student code firstname surname birthdate contact firstname contact surname 
1234   John  Doe 19/09/2000 Jane    Doe 
1234   John  Doe 19/09/2000 Harry    Doe 

Answer 1

可以使用string_agg功能。 類似這樣的：

select student.code as "student code", student.firstname, student.surname, student.birth_date, string_agg(concat(contact.firstname, ' ', contact.surname), ', ') as "contacts" 
from 
student 
join "studentContact" on student.id = "studentContact".student 
join contact on "studentContact".contact = contact.id 
group by student.id