使用JOIN多对多表进行SQL查询

Question

I have three tables (simplified):

Item (Id, ItemName)

1 Item1
2 Item2
3 Item3

Supplier (Id, SupplierName)

1 Suppler1
2 Suppler2

SupplierM2MItem (ItemId, SupplierId) – foreign keys

1 1
1 2
2 1

I need to get all suppliers for all items like this:

Item1 Supplier1
Item1 Supplier2
Item2 Supplier1
Item3

I believe it's not hard to achieve this but I can't. Can you please help

Answer 1

The right solution uses outer joins:

SELECT I.Item, S.Supplier
FROM Item I LEFT JOIN
     SupplierM2MItem S2I 
     ON I.Id = S2I.ItemID LEFT JOIN
     Supplier S
     ON S2I.SupplierID = S.ID;

Answer 2

I think it's an inner join plus an outer join. Try this:

SELECT I.Item, S.Supplier
FROM Supplier S
LEFT OUTER JOIN
SupplierM2MItem S2I 
ON S2I.SupplierID = S.ID
INNER JOIN
Item I
ON I.Id = S2I.ItemID