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“Beginning Visual C# 2005 Express Edition Video Series” - page 69 / 73

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Relationships

In a Relational Database, there might be many tables, each one linked to other tables by a relationship. A relationship means that for one row in one table, there might be one or more rows related to it in another table. For example, one table might contain companies, and another table called employees. One column in the Companies table is CompanyID, which would be the Primary Key. In this case, the CompanyID is just a number that uniquely identifies this row in the table ... there can't be two Companies with the same CompanyID. Each row in the Employee table will have a corresponding CompanyID field, which makes it related to the Company table. This CompanyID field is called the Foreign Key.

SQL Statements

You can retrieve values from the database using SQL statements, which stands for Structured Query Language. SQL is like a programming language for databases. For example, this statement would retrieve all the rows from the Company table where their headquarters were based in Texas:

SELECT * FROM Customers WHERE State = 'TX'

And here is a statement that might update one Company's city, state and zipcode:

UPDATE Customers SET City = 'Burbank', State = 'IL' and Zipcode = 60459

While this might seem like a lot of information, it’s actually just the tip of the ice burg. We may want to create our own database to store information collected from a Guest Form on a web site, or to store our company's products and pricing information, or any thing else we can imagine.

Supplemental Readings for the Express Edition Videos Copyright © 2005 LearnVisualStudio.NET

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