SQL 连接 3 个表，将重复的行加在一起

Question

我在解决这个问题时遇到了一些问题。

"Choose all people and their orders, it's important that you show their name, id - the products name and the amount. If a person has made 2 orders with the same item, you want to only show 1 order, but add together the amounts from both orders."

这是我目前所知道的，但我无法理解如何让多个订单只显示为 1，并将金额加在一起：

SELECT p.navn, p.id, v.varenavn, o.antal
FROM Vare as v
INNER JOIN Ordre as o
   ON v.vareid = o.v_id
INNER JOIN Person as p
   ON o.p_id = p.id

这些是表格：

变化：

create table Vare(
    vareid int identity(1,1) primary key,
    nummer int,
    varenavn nvarchar(100),
    højde int,
    vægt int,
    pris money,
    dato nvarchar(20),
    datotil nvarchar(20),
)

订单：

create table Ordre(
    ordreid int identity(1,1) primary key,
    dato date,
    tid int,
    antal int,
    totalpris money,
    betalingsfrist date,
    rabatgruppe int,
    v_id int foreign key references Vare(vareid) not null,
    p_id int,
)

人：

create table Person(
    id int identity(1,1) primary key,
    navn nvarchar(30),
    vejnavn nvarchar(50),
    postnr varchar(10),
    bynavn nvarchar(50),
    tlf int,
    kategori int,
)

Answer 1

你可以试试。

sum 所有 antal 和 group by 订单。

SELECT p.navn, p.id, v.varenavn, SUM(o.antal)
FROM Vare as v
INNER JOIN Ordre as o
   ON v.vareid = o.v_id
INNER JOIN Person as p
   ON o.p_id = p.id
GROUP BY 
    p.navn, p.id, v.varenavn

SQL 连接 3 个表，将重复的行加在一起

SQL Join 3 tables, add together duplicate rows

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