Programming :: Database Design Using IDs As Opposed As Candidate Keys As Primary Key
Jul 27, 2011
Self learner developer since about 2 years, I'm trying to understand deeper how to design a database in the best and most efficient way possible.Reading about UML design, I've found this: Do not automatically add ID numbers(surrogate keys) or substitute keys to a table until you are sure that:
-There is at least one candidate key (before the surrogate is added),
-the table is a parent in at least one association, and
-there is no candidate key small enough for its values to be copied many times into the child table.
Until then, I've always did this (I mean using ID) to identify my rows.So my questions are:
1. Why should we avoid using ID to identify rows?
2. Candidate keys add some weight to our database, and this can huge if we have millions of records, so why should we use these over surrogate keys?
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Sep 9, 2010
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May 2, 2010
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Is there a way to correct this?
Desktop Running Gear
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[Code].....
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Code:
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[Code]......
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<?php
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Heres the HTML code
<html>
<head>
</head>
<body>
<body bgcolor="#6881bb">
<center>
[Code]....
At the moment when i click the button, no matter what I enter every students marks appear on the screen.
I think, but obviously dont know for sure because if i did i would know how to solve the problem, the code that i need to change is in green.
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Code:
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b) How can i remove it,
I already have
Code:
sed '/^$/d'
c) Will this effect the file by any means (If I am guessing properly, this is the eof notation)
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Here's what I have so far:
Code:
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