Two tables having many to many relationship can not be linked together directly. They need a third table which is a link table / bridge table to link the two tables.
Ex – Table Book , Table Authors
A Book can have more than one author and an author can write more than one book.
To link these two tables a third table Book_Author is needed which stores the primary keys of the two tables as Foreign keys.
Table Book_Author Columns Book_ID(FK), Author_ID(FK)
All the existing combinations of Books and Authors are stored in this third table.
Category: Data Modeling
Bill Inmon Vs Ralph Kimball
In the data warehousing field, we often hear about discussions on where a person / organization’s philosophy falls into Bill Inmon’s camp or into Ralph Kimball’s camp. We describe below the difference between the two.
Bill Inmon’s paradigm: Data warehouse is one part of the overall business intelligence system. An enterprise has one data warehouse, and data marts source their information from the data warehouse. In the data warehouse, information is stored in 3rd normal form.
Ralph Kimball’s paradigm: Data warehouse is the conglomerate of all data marts within the enterprise. Information is always stored in the dimensional model.