1 00:00:00,180 --> 00:00:03,990 Back in lesson one and two, one of the tables in the zoo database we 2 00:00:03,990 --> 00:00:08,850 talked about, was the diet table which describes which foods each species eats. 3 00:00:08,850 --> 00:00:12,850 We looked at three ways we could store multiple foods, for a single species. 4 00:00:12,850 --> 00:00:14,450 As multiple food columns and 5 00:00:14,450 --> 00:00:19,050 one row per species, as a single column with foods separated by commas. 6 00:00:19,050 --> 00:00:22,410 And has separate rows, for each food comma species pair and 7 00:00:22,410 --> 00:00:25,690 I mentioned that this form, has some big advantages over the other two. 8 00:00:25,690 --> 00:00:29,440 It works better with drawings, it works better in comparisons and 9 00:00:29,440 --> 00:00:33,150 you don't have to know in advance how many foods there are, and we also looked 10 00:00:33,150 --> 00:00:37,390 at these two tables of donors to the zoo and their phone numbers. 11 00:00:37,390 --> 00:00:40,380 In order to avoid duplication, we split the information that 12 00:00:40,380 --> 00:00:44,120 was in one object or it's record, into two separate tables. 13 00:00:44,120 --> 00:00:47,340 In database jargon, these are called normalized forms and 14 00:00:47,340 --> 00:00:49,920 the others are denormalized forms. 15 00:00:49,920 --> 00:00:53,220 Normalization is the central idea in database design. 16 00:00:53,220 --> 00:00:56,100 Normalizing involves making the relationships among the tables in 17 00:00:56,100 --> 00:00:59,390 your database, match the relationships that are really there amongst 18 00:00:59,390 --> 00:01:00,910 the various pieces of data. 19 00:01:00,910 --> 00:01:03,640 There's a bunch of database theory behind this idea. 20 00:01:03,640 --> 00:01:07,240 I put a link in the instructor notes to a paper with lots of details about it. 21 00:01:07,240 --> 00:01:09,740 Up ahead, I'll just tell you the most relevant highlights.