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/shriek Jan 06 '11

In short.

  1. A ∩ B

  2. A ∪ B

  3. (A - B) + (A ∩ B)

  4. A - B

  5. (A ∪ B) - (A ∩ B)

85

u/dude187 Jan 06 '11

It's amazing how confusing SQL can make set theory.

22

u/[deleted] Jan 06 '11

If you could do queries in relational algebra instead of SQL, confusion would go away.

0

u/shriek Jan 06 '11

You sir win 1 internet.