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mysql custom global defined variable

+1 vote
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In my database design, I tend to store some variable that is meant to be acting as a ROLE or TYPE as SMALLINT. For example :

CREATE TABLE `house` (
   `id` int(11) NOT NULL AUTO_INCREMENT,
   `type` smallint(11) NOT NULL,
)

And in php, I do

define('HOUSE_SMALL_TYPE', '0');
define('HOUSE_MEDIUM_TYPE', '1');

So in php, in SELECT queries I do :

$this->db->query("SELECT * FROM house  
                    WHERE type=?;", HOUSE_SMALL_TYPE);

My questions are :
1. In the php part, is there is a better way to do this ?
2. In the mysql itself, does mysql also has global define functionality (like the define in php) ? I also want to do kind of SELECT * FROM house WHERE type = HOUSE_SMALL_TYPE in mysql query.

posted Mar 13, 2013 by Salil

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1 Answer

0 votes

Question 1:
I see no possible improvements, you could however use an array with values instead of constants, but that's rather a personal choice as I don't like constants that much, unless you are on your own namespace.

My example implementation:

$houseTypes = array(
        'house_small_type' => 0,
        'house_medium_type' => 1,
        etc.
);

Question 2:
You could use ENUM data type, but it has quite a few disadvantages:
1- Translation could be tricky to implement
2- DDL shouldn't be used for data!
3- Updating or deleting values can leave your old records in an inconsistent state

You can also use SET to set variables, I've never used them but I think they could work in your case:
http://dev.mysql.com/doc/refman/5.5/en/user-variables.html

answer Mar 13, 2013 by Salil Agrawal
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