Can a junction table (join table) also be used for a one-to-many relationship?

Question

According to the definition, a Junction Table (bridge table/link table) is used for many-to-many relationships, when used like this:

CREATE TABLE Users
(
UserLogin varchar(50) PRIMARY KEY,
UserPassword varchar(50) NOT NULL,
UserName varchar(50) NOT NULL
)


CREATE TABLE Permissions
(
PermissionKey varchar(50) PRIMARY KEY,
PermissionDescription varchar(500) NOT NULL
)


--This is the junction table.
CREATE TABLE UserPermissions
(
UserLogin varchar(50) REFERENCES Users (UserLogin),
PermissionKey varchar(50) REFERENCES Permissions (PermissionKey),
PRIMARY KEY (UserLogin, PermissionKey)
)

But couldn't it also be used just as easily for a one-to-many relationships, as in this example in which one user is associated with many orders:

(I don't understand databases well so please correct me if I have misunderstood something.)

CREATE TABLE Users
(
UserLogin varchar(50) PRIMARY KEY,
UserPassword varchar(50) NOT NULL,
UserName varchar(50) NOT NULL
)


CREATE TABLE Orders
(
OrderKey varchar(50) PRIMARY KEY,
OrderDescription varchar(500) NOT NULL
)


--This is the junction table.
CREATE TABLE UserOrders
(
UserLogin varchar(50) REFERENCES Users (UserLogin),
OrderKey varchar(50) REFERENCES Orders (OrderKey),
PRIMARY KEY (UserLogin, OrderKey)
)

Answer 1

There is not any reason why a junction table couldn't be used for a one-to-many relationship. The question is usually one of performance. Why make the database join an additional table when it is unnecessary?

Answer 2

Yes, but then you leave the check that it's not many to many to the application, instead of enforcing it inside the database.

Answer 3

Once you've built a table, it really doesn't have a type of "Junction" table, "associative" table, "join" table -- it's just a table.

We use these terms to describe a specific reason why an entity (and resulting table) was initially created. Associative entities are created, initially, to resolve a many-to-many situation. But these tables quite often have attributes of their own (such as the time of the association, a reason for the association, etc.). So SQL Server, Oracle or your code has no reason to know why a table was created...just that it's a table.

From a technical point of view, there really isn't any difference between an associative table and any other table.

So these tables can fill any role that any other table can fulfill. There are no rules around how other tables can also be related to them.