As a server side programmer you are going to be spending a lot of time working with data that is pulled from the database and in order to make sure that you do not have any loose ends it is a good idea to handle this situation with a class. This article is not going to cover how to code a data class nor is it going to help you create a specific data class. This article is here to show you how to make your data redundant and error proof.
Pulling all of your information
When pulling the information off the get go you are going to want to do one thing and one thing only: query all of the data that you can use in the class. The query is going to take place inside of a function and will most likely be used every time that you are in need of the data in the database. Once the query to obtain this information has taken place then you are going to either have results or no results and the easy way to check is simply by checking the number of rows returned.
Say we were trying to access user information for a user page. It would be a good idea to query and make sure that all of the information is available. In this query we are most likely going to be joining up to multiple tables because having all of the user information stored in one table would create a fair amount of overhead and would increase the time it took to go through the table. For this reason we break things apart.
An Example Of Database Tables
A well structured database table is going to be pulling from an auto incrementing ID. This auto incrementing id is going to be found on every table but since we can not just assume that if we insert a record into tbl_user and tbl_user_profile at the same time we are going to get ID’s that match properly. Because this is a flawed way of looking at the table set up we are going to use the auto incremental ID from the tbl_user and plug this into a new column on the other user tables. This way we can simply join the tbl_user.user_id to tbl_user_profile.user_nid. Now that we have a relationship in the database that will work and is pretty redundant in theory we are still going to have to deal with the situation of a table not being created properly upon user registration and thus we are lead to…
Enforcing Existing Tables
Remember back up at the top when I was talking about the query all function either working or not working? Well this function upon returning zero rows will tell us one of two things. (Assuming the SQL was written properly.) The first thing that it will tell us is that this user does not exist, and the second thing is that the user is missing a table. This could mean that something was deleted, or maybe the table was recovered in backup at a later date and there was a record missing. Either way we know that by checking the user table for the users existence we are able to confirm that we are dealing with missing data and this is where the checking functions come into place.
In a well written data handling class there will be functions that exist to pull results from each of the individual tables. These functions are excellent for checking that a user does exist in the following table and are a great way to quickly and easily pull sections of content based on the user which are handy when loading content on an interval via AJAX. But now we are getting a little off topic. Creating a function that can pull information and return a number as a status and creating another function that will insert defaults into the table is an excellent way to make sure that you do not lose data and that all of the data is being pulled properly.
Recap
When using the class you are most likely just going to need to get the information which means that you will be using a function that behaves like the queryAll that I was talking about. If the user does not exist then you can simply return false.
The next step is to create functions that will check individual tables based on that original tbl_user.user_id (or whatever yours is) starting with the initial tbl_user which the rest of the tables are based on. This will tell you if it was created in the first place or not.
If we have gotten far enough to know that the user does exist and the user simply doesn’t have a record in one of the tables then we can query each of the tables and find out where the record is missing. Now that we know the table we can simply insert blank data into the table and maybe send a notification to the user that they may need to update a certain part of their profile.
Knowing when we have an error in table creation
Through this data class it is just a matter of adding in an error log message to let the administrators tell if the application has a bug in it but this shouldn’t be a problem if you are handling proper inserts and updates through SQL and checking for an affected row upon creation.