Welcome to Understanding Data Types Part 2. In Part 1 I kind of kicked off this conversation about data types and some of the most basic aspects of them and in here in Part 2 we're just going to continue. So let's continue right where we left off. Now how do you choose which data type to use? Well there's a little formula here. First of all you base it on knowledge. How much do you understand about the data types? Now this is kind of interesting because the second aspect is experience. But these are not necessarily in the order that you see because knowledge will feed experience and experience should feed knowledge. But strangely enough with a lot of database developers that just does not happen. And here's what I mean by that. For example I have a knowledge that the long integer type is a number type. And so I can use long integer anytime that I want to store numbers and it'll work, it'll work just fine. And so my experience then becomes anytime I need to use a number I use the long integer data type. Well that's not good because I'm probably wasting memory space when I'm using small numbers. I could use the byte data type but instead I'm using the long integer. And keep in mind Access we'll choose the numeric data type then we'll choose a field size property that limits that data type to like byte, long integer, single that sort of thing. Okay. But you'll see that a little bit later on, don't let me confuse you with that. Here's what I want to warn you about. Just because a data type works you need to go back from time to time and reacquaint yourself with the various aspects of each one of the data types. How much memory they consume, exactly what size numbers you can store in that particular data type to make sure that you're not inefficiently storing data or putting a load on your server. Because one of the things that you always want to do with a database, because you're going to be storing a tremendous amount of data is you want to tweak as much performance and efficiency out as you possibly can. Now you can see a video entitled Data Types and that will be a two parter as well, later on in the course. Again the title of the video will just be Data Types, Part 1 Data Types, Part 2. And I'll give you a lot more details about each of the data types that are available to you in Access, how much memory they take to store the data and exactly what data you can store in that data type. Now a question always comes up is, when I'm trying to determine what data type to use, how exactly do I go about that? And this is another one of those situations where I can show you a table that I designed, I can show you the data types that I gave the various fields. And then we can bring other database developers in and they'll begin laugh and chuckle amongst themselves because I've done something differently than they would do it. There's a lot of different ways to get to the same place, some are absolutely positively better than others. Some are open to debate and some are just you know worth fighting. Okay. So first of all what kind of data do you want to allow in the field? Is this a field where you want to allow users to put in numbers or characters? Or do you want to restrict them to certain things? And so that's one of your first choices. Then how much storage space do you need? Now that's going to determine the data type and the field size property that you use. If I'm going to store let's say the franchise numbers of, of my little pizza franchise. But I've only got ten franchises right now and it's, it's only going to be about 350 years before I ever have more than 254 then I can use the byte field size property on a numeric data type. Because that lets me store between 1 and the number 254. So that's pretty good or it's 255 something like that, I'm going blank because I'm in a live situation now okay? So don't hold me to it. But trust me as long as I'm not going to exceed that number on the high end then I'm going to be okay. As soon as I do I'll get an overflow error. Okay. But I don't want to tell it long integer and store a whole bunch of space and memory out there that I'm never going to use. Now what type of operations will I perform on the data? And for example do I want to sort or index the field? If the data type is OLE objects, I can't index on that and I also can't sort on that. And another close cousin to that question is how do I want to sort the values? And here's a good example. If I set a column or a field up to be a text data type, I can sort it later. But if I put numbers in there they're seen as text. And so if I have numbers you know 1 to 300 this is how it's going to store them. Okay. 1 will be first, 2, 3, 4, 5, 6, 7, 8, 9 10, 11 and so forth. Okay. You'll see 1 then 10 then 100 then you'll see 2. Then you'll see 2, then you'll see 20 then 200 and 3 and so forth. Because it's seeing them as text and it's taking them all together. It's not going to organize them the same way as numbers. If you've ever worked with numbers in any kind of application before and you got 1 and then 10 and then 2, you're like wait a minute how did this get out of order like this? So it goes 1, 10 2, 3, 4, 5, 6, 7. And again if you got a 20 in there it messes up. Then you're looking at numbers that have been sorted as text. So you got to watch for those kinds of things. So you'll these quick and experience will teach you. But if you want those to be sorted as true numbers then you want to make that a numeric field. Those kinds of little issues will pop up for you from time to time and you'll just have to get used to dealing with those and you'll get better and better at this. Okay. But understanding data types is a key piece of functionality in knowing how to design really well built efficient databases.
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