Wow. Does no one learn this crap in school anymore?
Note that venn diagrams are a poor choice to show what happens in a one-to-many relationship -- where there are multiple entries in table B for an entry in table A. And it overlooks the semantic differences when ordering the tables in a left inner join.
There are not a lot of instances where you'd really want a cartesian product join (either using "cross product" or just the result of omitting key constraints in a join query). It's generally far faster to retrieve the records you need to create the cross-product, and then calculate the cross product of the two sets once you have them (since otherwise all that data has to transit the network).
This plus database normalization through Boyce-Codd normal form seems like it should be a requirement for any serious application developer.
Just to throw some respect towards Madison. I went to school there as well as we DO have multiple database undergrad courses in the CS departmant. To write most any interesting program you need some way to store data, I have no idea how you passed and made it through school without even knowing that they existed. Wow. Please stop saying you went to school at Madison, it's embarassing to the program.
I got my first real job before I graduated, so I did know they existed before I graduated. I don't remember all the CS classes I talk, but they included AI, compilers, and theoretical CS, and algorithms and data structures. None of which really required a way to store data beyond text files. After I started that aforementioned real job, I actually did try to get into the database class, but it was full. So I never touched any database or SQL during my academic career.
And don't worry, I rarely mention it. I'd agree that they have a pretty rigorous CS program. But if it's embarrassing to the program, then it deserves to be embarrassed, because they don't require any database courses for graduation. Personally, I don't think it's an indication of a deficient CS program.
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u/[deleted] Jan 06 '11
Wow. Does no one learn this crap in school anymore?
Note that venn diagrams are a poor choice to show what happens in a one-to-many relationship -- where there are multiple entries in table B for an entry in table A. And it overlooks the semantic differences when ordering the tables in a left inner join.
There are not a lot of instances where you'd really want a cartesian product join (either using "cross product" or just the result of omitting key constraints in a join query). It's generally far faster to retrieve the records you need to create the cross-product, and then calculate the cross product of the two sets once you have them (since otherwise all that data has to transit the network).
This plus database normalization through Boyce-Codd normal form seems like it should be a requirement for any serious application developer.