SQL - Primary And Foreign Keys
So if your here on this post you're after understanding the mysteries of Primary/Foreign key relationships. Well let me tell you they are an art form not an exacting science something at first you may not appreciate until you deal with your own database schema's.
Basically, all databases need them. I have had arguments with people in the past saying "you don't need them" I normally let them have just enough rope to hang themselves but make sure I have got the scissors on standby to save the day when they discover the need for them when duplicate orders or duplicate customers start cropping up in thier "brand new" database system.
I cannot stress to you all the importance of primary keys.....foreign keys are important but in my line of work (BI) I can get away without using them as much. But Primary Keys are paramount in a design as they make them unique and indexed. The final point about indexes will be covered in more detail on a separate video as the goal here will be to understand the symbiotic relationship these primary/foreign key elements have for each other.
This is one of many videos which can be seen at PCTeach.me. Come join the gang!
На этой странице сайта вы можете посмотреть видео онлайн SQL - Primary And Foreign Keys длительностью часов минут секунд в хорошем качестве, которое загрузил пользователь PCTeachME 16 Октябрь 2009, поделитесь ссылкой с друзьями и знакомыми, на youtube это видео уже посмотрели 135,890 раз и оно понравилось 209 зрителям. Приятного просмотра!
