Improving SQL Queries - php

Question

I have recently designed a website that used a lot of queries. During the time I was developing my website I came across an issues which was very time consuming and frustrating.
So the problem was that at a certain point I wanted to add an additional feature to the website where it would affect most on my queries and I needed to change most of them to make the feature work. So let me give an example: Lets says I have a users table, and I didn't add a column to check if a user is banned. Now I added the column "banned", and now the problem was that, I need to arrange all the other queries to check if the user is banned first. I hope that makes sense.
So my question is, is there a way I could minimize that work and instead of going through all the queries and revising them (To add the is user banned), I could instead add that feature once and the queries would work? Basically how can I improve?
I hope this makes sense and if not I would try my best to explain it further.
Any help would be greatly appreciated if it could help improve my coding knowledge.
PS. I am using SQL and PHP. If there is something better than SQL that would fix this problem, suggest away.
Thank you

Answer 1

I understand your problem. You have some column-rule. Which is globally used in all app. For example in my case there was 'status' column, and there were some logical meaning called 'important', which worked if column had one of the certain values in the set.
So, everywhere, to check if status is 'important', I needed to write:
WHERE `status` IN('INCIDENT', 'ERROR')
If I needed to add for example 'FLAGGED' to list of important statuses, I needed to rewrite all SQL queries:
WHERE `status` IN('INCIDENT', 'ERROR', 'FLAGGED')
Once I got tired of this. I decided to write a MySQL function which did this work. Called it IS_STATUS_IMPORTANT(status).
But this solution failed the test because it slowed down performance - it did not allow MySQL to use indexes properly.
I finally solved this problem by creating some set of app-global conditions, lets say:
class DbHelper {
public static function importanceCondition($column_name) {
return $column_name . " IN('INCIDENT', 'ERROR') ";
}
}
And now all over app I write:
$sql = 'SELECT * FROM blah .... WHERE ... AND ' . DbHelper::importanceCondition('x.status');
If I need to change some the logical condition I do it in one place and it applies all over the application.
In your case you could add some function
class DbHelper {
...
public static function validUserCondition($user_alias) {
return " ({$user_alias}.deleted = 0 AND {$user_alias}.banned = 0) ";
}
}

Answer 2

Why don't you check this during the login of the user? If (s)he is banned, the logon fails and all further queries are impossible to be executed in the first place.
Generally you should never spread the same logic to multiple code locations because of this multiple effort this will cause whenever you want to adjust something.
Create reuse methods where you have reuse. This could be even reuse to enhace a given SQL (prepared) statement with another WHERE condition or a method that performs the SQL request itself.

Answer 3

I understand your problem there are some easy solution for this using ORM (Object Relational Mapping) to query which supports multiple DB like (SQL, mysql, Oracle DB, NoSql...)
PHP ORM's like - Doctrine, Propel
ORM Better support for most of PHP Frameworks
Which has the better way you work with queries
Less complex in coding which splits up functionalities into classes
Easy to manage relations in table
I hope this will help you for modifying queries with less time and great performance

Answer 4

I assume you have code included in every page to make sure that the user has logged in sucessfully.
If that is the case then all you should need to do is change the login script to reject banned users, every other page will therefore work as it is and reject any users that are not logged in and none of the queries on these other pages would need to be changed.