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132notes

# 132notes - IS <= every key S-> D I-> B IS-> Q B-> O(IS =...

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IS <= every key S -> D I -> B IS -> Q B -> O (IS) + = ISDBQO (include all the ones that FIND BCNF, LOSSLESS JOIN, DEC. B O ISQD CHOOSE S->D LEFT = SD, RIGHT = B O ISQ CHOOSE I->B LEFT = IB, RIGHT = OISQ I + = IBO I -> O IMPLIES BY I->B->O (STILL A VIOLATION) LEFT = IO, RIGHT = ISQ S + = SD Q + = Q DRAW LIKE A TREE, INCREASING ON RIGHT SIDE 1. DEP PRESERVERING? SD IB IO ISQ SD IB* IO ISQ B B+= BO (NOT RESERVED) IS THE FIRST STEP REDUNDANT? CHECK IF IMPLIED BY OTHER FD’S 1. 3NF - REDUNDANT FDS IF D IS THE ONLY D ON THE RIGHT HAND SIDE, SO IT IS THE ONLY WAY TO GET IT. CANNOT BE IMPLIED. SO GOES FOR THE OTHERS, THE RIGHT HAND SIDE AREN’T COPIED I+ = ibo S+ = sd No redundancies FUCK YEAH FOR 3NF TAKE SD IB ISQ BO (THE LEFT HAND SIDE AND GROUP THE RIGHT HAND SIDE) ARE THERE ANY ATTRIBUTES NOT COVERED BY THIS? BROKER B, OFFICE O, INVESTOR I, STOCK S, QUANTITY Q, DIVIDEND D MAKE SURE IT CONTAINS A SUPERKEY. ONE OF THOSE MUST BE A SUPERKEY, OHERWISE, YOU HAVE TO ADD ANOTHER KEY. IN THIS CASE WE KNOW THAT IS IS A KEY, SO ISQ IS A SUPERKEY

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