From the course: SQL Server 2008 Essential Training

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Defining keys

Defining keys - SQL Server Tutorial

From the course: SQL Server 2008 Essential Training

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Defining keys

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One thing you should do on all of your tables, at least as a general rule, is defined what's called a primary key. This is a way that's going to identify how do we get to an individual role. One value that would always take us to just one row in that table. And your primary key can be any of the columns that you actually have defined if that makes sense. Sometimes it does, sometimes it doesn't. If I look at my Product Table, for example I have ProductID, ProductName, UnitPrice and UnitsInStock, and let's say that my business process was such that ProductIDs were decided around a conference table and manually entered into the database. Well I could say then ProductID should be my primary key. One ProductID should always identify a row in this table in this database. Well I have it open in Design. I can right- click the column and just say Set primary key. Notice what happens to the Allow Nulls column when I do this. It's going to turn it off because when you think about it, it doesn't…

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