Database Design 40 - Data Types — Transcript

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1. 0:00hey guys welcome back this video we will
2. 0:02be
3. 0:02discussing data types I almost forgot
4. 0:06there anyways what a data type is is
5. 0:08when you create a
6. 0:10column every single value in that column
7. 0:13has to be of a certain data type so you
8. 0:17need to tell that column when you create
9. 0:19the database what data type it is to be
10. 0:22also when you're designing you usually
11. 0:25put the data types there as well so that
12. 0:27way you have an idea of how your
13. 0:29database is going to work work so
14. 0:31there's three main categories of data
15. 0:33types and the naming conventions or the
16. 0:36names of these data types from one
17. 0:39database management system to another
18. 0:41database management system might vary a
19. 0:43little bit but in general they're
20. 0:45organized into three main kinds that's
21. 0:49date numeric and
22. 0:53string so basically we're going to be
23. 0:56going over these in a little bit of
24. 0:57depth we're not going to go super in
25. 0:59depth because right now you just need to
26. 1:01understand what these are and just
27. 1:03understand that your database
28. 1:05application might be slightly different
29. 1:07from others let's start from the bottom
30. 1:09up just to make things fun string string
31. 1:12is any characters or like letters so
32. 1:16basically you put these within quotes
33. 1:19so
34. 1:22hey this is an example of a string even
35. 1:25a number within quotes can be used as a
36. 1:28string and this this would be used as a
37. 1:31string basically
38. 1:33the uh the three doesn't have any
39. 1:36mathematical value unless it's converted
40. 1:39to
41. 1:40numeric within string you'll often have
42. 1:43some subcategories you'll have something
43. 1:46that's either Char or varchar which
44. 1:50those just mean character or variable
45. 1:53character what that means is it's just
46. 1:56like um a list of characters the
47. 1:58character or char
48. 2:00usually is stuff that's set in length so
49. 2:03like a phone number or a zip code
50. 2:05something that doesn't change sizewise
51. 2:09so basically with a Char you'll you'll
52. 2:10have it something
53. 2:12like CH 8 and every single value within
54. 2:18that Char column is going to be stored
55. 2:21as a individual characters now even if
56. 2:24you don't put eight characters let's say
57. 2:26you put six then there's going to be two
58. 2:28blank characters in there so they're all
59. 2:30stored as eight varar on the other hand
60. 2:34is variable basically meaning that the
61. 2:37size can change you can have anywhere
62. 2:39from zero up to eight there's also often
63. 2:44the subcategory or subd dat type of text
64. 2:47which is often used for larger things
65. 2:50such as comments messages and so forth
66. 2:54that's basic summary of the string data
67. 2:57types as for numeric data types
68. 3:00these are
69. 3:02numbers that's different than this this
70. 3:04is a string that has a number in it
71. 3:07that's used differently than the numeric
72. 3:09data type the numeric data type doesn't
73. 3:12have quotes it's just the numbers that
74. 3:15you're using just like string there's
75. 3:17often some subcategories of decimal and
76. 3:20then floating point or
77. 3:22double
78. 3:23decimal Works in base 10 now I know we
79. 3:28haven't really gotten much into
80. 3:30bases and I'm just going to put date
81. 3:32back up here since we haven't got that
82. 3:35yet but I think it's really important to
83. 3:37know and in fact I've made a lot of
84. 3:39videos over binary hexadecimal and stuff
85. 3:42basically different numbering systems
86. 3:44that use different bases well decimal
87. 3:47uses base 10 it's the number system
88. 3:49we're used to counting in you know 0 1 2
89. 3:523 4 5 6 7 8 9 and then it goes back to
90. 3:5710 11 12 13 14 if it's base 10 that's
91. 4:01what de means in decimal well there's
92. 4:04also
93. 4:05binary so we
94. 4:08have decimal and then we have a
95. 4:12binary decimal is base 10 binaries in
96. 4:15base two so binary we only have the
97. 4:19options of zero and one now you don't
98. 4:22really need to understand how to like
99. 4:23calculate in binary but if you want to
100. 4:25know that I do have videos for that but
101. 4:27just know when we're working with
102. 4:28decimal it is working with a base 10
103. 4:32system when we're working with floating
104. 4:34points we're working with binary which
105. 4:37is stored differently it's stored in
106. 4:39binary and then you can have it
107. 4:41presented as decimal for math or
108. 4:45whatever so what's really the difference
109. 4:47do you use decimal or do you use
110. 4:49floating
111. 4:50points it just kind of really depends
112. 4:53decimal generally is more accurate on
113. 4:57mathematics to a point there are
114. 4:59problems that can come up with decimal
115. 5:01but you'll just have to research those
116. 5:03but
117. 5:04basically uh this one has some errors
118. 5:07binary it has problems with certain
119. 5:10mathematical equations or numbers for
120. 5:14example when we want to store
121. 5:181/4 it's stored like this we have
122. 5:230 Z
123. 5:25one and the way this kind of works is we
124. 5:28have anything after the
125. 5:31point that divides the number basically
126. 5:36in half so we would have half but we
127. 5:38don't have half so we have half of a
128. 5:40half
129. 5:411/4 kind of makes sense so the the place
130. 5:44values would be this one right here
131. 5:47would be uh we'd have
132. 5:49half this place value would be 1/4 and
133. 5:54then anything after that would be
134. 5:571/8 and anything after that would be
135. 6:00116th so right now way we have it we
136. 6:04would take 12 multiply it by 0 to get
137. 6:09zero because we don't have anything
138. 6:10there we take 1/4 multiply by one since
139. 6:13we have it there we' get 1/4 0 0 we add
140. 6:18those up we get 1/4 basic uh adding and
141. 6:23multiplying to understand how it works
142. 6:26but when we have a number such as
143. 6:280.1
144. 6:31in decimal that is basically impossible
145. 6:35to store in binary simply because we're
146. 6:38working in a base 2 system and we can't
147. 6:42get 2.1 very easily because 1/8 that
148. 6:46doesn't quite cut it you'd have to
149. 6:48basically have a combination of a bunch
150. 6:51of different fractions to get as close
151. 6:53as possible 2.1 but you can never really
152. 6:55get there perfectly so that's a problem
153. 6:57with the floating points
154. 7:00so if you needed to store something like
155. 7:01that you would if it needs to have that
156. 7:04accuracy you would have to have it
157. 7:05stored as a decimal which stores it
158. 7:10differently that was a lot sorry if I
159. 7:12completely overwhelmed you with that
160. 7:13number stuff and if I did don't even
161. 7:16worry about it that was a little too
162. 7:17fast if you need it slower please check
163. 7:20out my introduction to Binary video it's
164. 7:24a super long video where I basically
165. 7:26explain it step by step so you
166. 7:28understand and then I have a couple
167. 7:30other videos adding and subtracting and
168. 7:32also fractions in a binary you will also
169. 7:36have an integer type which will only
170. 7:38store numbers that don't have any
171. 7:40decimals after them so only whole
172. 7:42numbers like 5 12 28 52 so forth with
173. 7:47numbers we also have to worry about
174. 7:48whether they are unsigned or signed if
175. 7:51they are unsigned numbers that means
176. 7:53that they can't be negative if they're
177. 7:55signed that means they can be positive
178. 7:57or negative you're probably wondering
179. 7:58why would you ever do that well if
180. 8:00you're working with something that
181. 8:01doesn't go negative well then you
182. 8:03wouldn't need to have that negative when
183. 8:05you have a signed number and it can be
184. 8:07positive or negative the range of
185. 8:11potential values stays the same but
186. 8:14since you include negatives the maximum
187. 8:17value is different it's not as high
188. 8:21think about if you have a range from 0
189. 8:23to a
190. 8:24th000 but then you include negatives now
191. 8:26you have from 500 to 500 that is going
192. 8:29to be told with the data type so you
193. 8:31might say something like
194. 8:34double
195. 8:36unsigned that would work as a number
196. 8:39that's enough for numbers I don't want
197. 8:41to talk about this anymore let's talk
198. 8:42about dates dates well there's couple
199. 8:46different things you need to know about
200. 8:47dates there's date then there's time
201. 8:51there's date time and then there's
202. 8:53timestamp so let's talk about date time
203. 8:55first because it makes sense the best it
204. 8:58basically just stores a dates such as
205. 9:00you know 02 for February then you might
206. 9:03have a colon you might have 22 for the
207. 9:05date 22nd and then a colon maybe
208. 9:101998 for 1998 the year then you have the
209. 9:14time which could be whatever it could be
210. 9:1712 30 22 which would be the seconds and
211. 9:21you might even be able to have some
212. 9:22milliseconds or micros
213. 9:24seconds that's how you would store a
214. 9:26date time the way it actually looks
215. 9:29might vary from database management
216. 9:31system to database management system
217. 9:33some might have colons between the
218. 9:35numbers some some might have hyphens or
219. 9:38commas or whatever doesn't really matter
220. 9:40I don't want you to think about that
221. 9:41right now I just want you to think about
222. 9:43the date being a date and the time being
223. 9:47a time date time being the combination
224. 9:50of a date and a time that's pretty much
225. 9:54that for dates the only other thing is
226. 9:56the time stamp the time stamp is an ex
227. 9:59exact moment in time that's recorded to
228. 10:02establish when something was created or
229. 10:05done it can be in milliseconds or it can
230. 10:08be in the month and the day and then the
231. 10:11second hour and then the seconds and
232. 10:13then the milliseconds or it can just be
233. 10:15a number of seconds so forth it varies
234. 10:18but anyways that's going to give you a
235. 10:20number when something was done it's
236. 10:23usually for something like when an
237. 10:25account was created or when a
238. 10:27transaction was done or when something
239. 10:29happened when you update a column that
240. 10:32Tim stamp will often
241. 10:34update and that's going to keep it to
242. 10:37like when that row was entered into the
243. 10:41database so if you enter a new row and
244. 10:44one of the columns is a timestamp it's
245. 10:47going to give you a value as soon as you
246. 10:49submit that and it's put into the
247. 10:51database the timestamps created and it
248. 10:53says okay this row was entered at this
249. 10:55time that's the main thing with um
250. 10:57timestamps so so basically we got three
251. 10:59types of data types we got
252. 11:02string um numeric and then date all of
253. 11:06those classifications have different
254. 11:09data types for each one but in general
255. 11:12as long as you know like the gist of
256. 11:14what is what you'll be fine you don't
257. 11:17have to worry too much because when you
258. 11:18get in actually programming a database
259. 11:20you will have more specifics on what
260. 11:22data types to use so you guys thank you
261. 11:25for watching sorry for rambling in this
262. 11:26video is a long one
263. 11:29peace out