Foreign key - A foreign key is a column that references another column, usually another primary key. In an upcoming video we will discuss primary and foreign keys in detail so you know more about what is allowed, how to design them, and how to implement them. Relationship - a term used to describe connections between data. Both primary keys and foreign keys are examples of constraints. Constraints - Rules that prevent certain data to be entered into a database. We use constraints to protect our data integrity. For example, we could say that we want every value for a column to be unique, but how do we enforce that? We have to use a constraint. Index - Put simply, an index is something we put on a column, or a group of columns, that improves performance when we SELECT data. We will be learning about all of the details of indexes in upcoming videos. Data types - Every column has to have a data type. This tells the database how to interpret certain data. For example, 2 and '2' are treated differently by the database. You can generally separate data types into 3 categories: string, numeric, and temporal. Now these are categories, so within each category there are specific data types, but we are going to get into all of that in future videos. Data types are important because it allows the database to know how to work with the data. In addition to this, they also work kind of like a constraint in that having data types on columns makes the database reject data that does not match what a column is supposed to be. So if we have a numeric column and try to put in the 'pie', it will not work. As you've probably noticed, a lot of what we have been covering comes back to the concept of integrity. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELP ME! www.patreon.com/calebcurry Subscribe to my newsletter: eepurl.com/-8qtH Donate!: bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: CalebCurry.com Facebook: www.facebook.com/CalebTheVideoMaker Google+: plus.google.com/+CalebTheVideoMaker2 Twitter: twitter.com/calebCurry Amazing Web Hosting - www.dreamhost.com/r.cgi?1487063 (The best web hosting for a cheap price!)

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