Can we have two foreign keys in a table in SQL Server?

Can we have two foreign keys in a table in SQL Server?

A table can have multiple foreign keys and no composite keys. A composite key simply means that there are two or more columns making up the key value. The set of columns in a foreign key references the values in a set of columns in another table (or, exceptionally, of another set of columns in the same table).

How many foreign keys can a table have?

253
A table can reference a maximum of 253 other tables and columns as foreign keys (outgoing references).

Can a table have two foreign keys and no primary key?

Yes, you can make one without a Primary Key (or, another option is a Compound Primary Key – making the two references a unique pair, and using that as the unique identifying key – but even this isn’t necessary (note: just because it “isn’t necessary” doesn’t mean it isn’t “good practice”; it wouldn’t generally be a …

Can a table have no primary key?

Every table can have (but does not have to have) a primary key. The column or columns defined as the primary key ensure uniqueness in the table; no two rows can have the same key. The primary key of one table may also help to identify records in other tables, and be part of the second table’s primary key.

Can foreign key be NULL?

Short answer: Yes, it can be NULL or duplicate. I want to explain why a foreign key might need to be null or might need to be unique or not unique. First remember a Foreign key simply requires that the value in that field must exist first in a different table (the parent table). That is all an FK is by definition.

Can a table have 3 primary keys?

A table can only ever have a one primary key. It is not possible to create a table with two different primary keys. You can create a table with two different unique indexes (which are much like a primary key) but only one primary key can exist.

Can a table have 3 foreign keys?

Answer: SQL Server 2014 and earlier versions, supports 253 as a maximum foreign key table references per table. However, this limitation, changes in SQL Server 2016. A table can reference a maximum of 253 other tables and columns as foreign keys (Outgoing Foreign Key References).

Can a table have all foreign keys?

A table may have multiple foreign keys, and each foreign key can have a different parent table. Each foreign key is enforced independently by the database system. Therefore, cascading relationships between tables can be established using foreign keys.

Can you have a foreign key but no primary key?

It is perfectly fine to use a foreign key as the primary key if the table is connected by a one-to-one relationship, not a one-to-many relationship.

Can a table only have a foreign key?

There is no problem having a table that consists of foreign keys only. In your particular example it would be OK to remove the OrderID. Relational theory states that each table should have a candidate key so, ideally, the business rule you mention would be in place to make the foreign key only table a “good” table.

Why foreign keys are not redundant?

Essentially, primary and foreign keys are used as a way to constrain or link related data in a database. This ensures that data remains consistent and that the database contains no redundant data. For example, if you delete a table (or even a row in a table) that other tables rely on, the redundant data is removed.

Can foreign key be duplicate?