MySQL notes

It has been some time since I took my intro to Relational Databases back in the spring of
07. So today I decided to do some research on MySQL and the database in general. So without further adieu, here are some helpful notes.

Data Types

  1. char vs varchar – If a string is inserted of 20 character in length is inserted into a char(30) field, it will take up 30 characters in the database. If that same string 20 characters in length is inserted into a varchar(30) field, it will take up just 20 characters of space.
  2. Int vs smallint – Smallint is used if your number will not exceed the range of -32768 – 32768. Int is used when the number falls between -2147483648 – 2147483648. It is also worthy to mention the other types of integers, tinyint, mediumint, and bigint

Normalization

Database normalization is quite possibly one of the blurriest areas for me. Going from teachers that profess a web site needs to be normalized to other teachers that say ‘if it works don’t fix it’ I have had to find a middle ground for now until I can make a decision and learn more about it. For most projects I do, I follow through to third normal form (3NF). This prevents from having redundancy, duplicate data, as well as prevents data anomalies from occurring. Data anomalies are incorrect/inconsistent data that is the result of updates or insertions that create “duplicate” records.

On another note, I just purchased a new MySQL book MySQL Crash Course by Ben Forta. It looks to be an excellent replacement for my current book. Just looking through the table of contents and reading a few pages, it covers way more than my previous book I purchased for my relational database class. So stay tuned for MySQL Notes ver.2.

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