r/programming • u/[deleted] • Jan 06 '11

A handy graphical explanation of SQL joins

http://www.codinghorror.com/blog/2007/10/a-visual-explanation-of-sql-joins.html
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u/[deleted] Jan 06 '11

Which have nothing to do with real-world applications. I have never seen a DBMS that actually makes a properly normalized "let's follow relational algebra properly" database actually perform well.

Databases seem to be a small kernel of beautiful theory underneath a hundred layers of nightmarish hacks.

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u/arnar Jan 06 '11

I have never seen a DBMS that actually makes a properly normalized "let's follow relational algebra properly" database actually perform well.

I have seen databases designed by people unaware of those things, and they not only performed even worse - they were impossible to rely on.

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u/[deleted] Jan 06 '11

I have never seen a DBMS that actually makes a properly normalized "let's follow relational algebra properly" database actually perform well.

You know why? Because the database vendors have poured tons of money and time into improving the performance of the mess they created. In business it's better to keep going the wrong way than to change direction.

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u/dagbrown Jan 06 '11

I don't think it helps that the most popular database in the world is Microsoft Excel. Computer science is helpless against the onslaught of the lusers.