MS SQL Server 2012 Guide for Beginners - Database Relationships - Part 2/5

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In this MS SQL Server 2012 video series, we cover the different types of Database Relationships in Microsoft SQL Server 2012. Database relationships refer to two columns in a database or databases reference each other. They are usually defined where a Primary Key is linked to a Foreign Key.

This five-part series covers the following:
- Part 1 – This part covers some terminology and one-to-many database relationship in SQL Server 2012
- Part 2 – This part covers the many-to-many database relationship in MS SQL Server 2012
- Part 3 – This part shows how to link databases using a Foreign Key (FK)
- Part 4 – This part continues demonstration of many-to-many database relationships and database linking
- Part 5 – This part continues demos of many-to-many database relationships using a database junction table

There are three types of Database Relationships in MS SQL Server 2012:
- ONE-TO-ONE: Not a very common database relationship. This is where one row in a table has only one matching row in another table. Typically used for splitting a table or for isolating part of a table for security purposes.
- ONE-TO-MANY: The most common database relationship, this is where one row in a table has one or more matching rows in a second table. However, one row in the second table will only have one matching row in the first. For example, for a Customer-Order database, one customer may have many orders, but one order will only have one customer.
- MANY-TO-MANY: In this relationship, a row in one table can have many matching rows in a second table and the second table can have many matching rows in the first table. In a Patient-Doctor database, one patient can have one or more doctors and one doctor can have one or more patients. This type of database relationship requires a third table which stores the information from both the first and second tables.

This video part (2 of 5) continues the demonstration of the one-to-many database relationship in SQL Server 2012. Then we define and demonstrates the many-to-many database relationship in SQL Server 2012 using a school database example (Student-Classes database).

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