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Should a data warehouse have foreign keys?
The reason for using a foreign key constraint in a data warehouse is the same as for any other database: to ensure data integrity. It is also possible that query performance will benefit because foreign keys permit certain types of query rewrite that are not normally possible without them.
Do Fact tables have foreign keys?
Each of the dimensional tables includes a primary key (product, time_code, customer, district_code), and the corresponding columns in the fact table are foreign keys. The fact table also has a primary (composite) key that is a combination of these four foreign keys.
How to create foreign key with Cascade delete in SQL Server?
A foreign key with cascade delete means that if a record in the parent table is deleted, then the corresponding records in the child table will automatically be deleted. This is called a cascade delete in SQL Server. A foreign key with cascade delete can be created using either a CREATE TABLE statement or an ALTER TABLE statement.
Why to use foreign keys with no action on delete or update?
The foreign key constraint even without ON DELETE / UPDATE CASCADE ensures that if you insert a value into the child table, that it has a correctly matching value in the parent table (or is NULL if the FK column is nullable).
Why do we need to use foreign keys?
If you have 1-to-many or many-to-many relations in database, foreign keys will be very useful. Find more information here – Referential integrity. Also they have some good actions – RESTRICT, CASCADE, SET NULL, NO ACTION; read this information in documentation. So, foreign keys and database itself can do some work for you.
How does the FOREIGN KEY constraint work in SQL?
To understand the concept of the FOREIGN KEY constraint in SQL, you can think of it as a reference link between tables that are known as the primary (or parent) and foreign (or child) tables. The foreign table references one or more columns (the primary key, which can be one or more columns) in the primary table; that is how the link is created.