Code for updating the database
Backward-compatible operations are all operations that change your database in a way that it can be used by the old and the new version of your application.That means that you can execute them during a migration step and don’t need to split them into multiple operations.These operations require a multi-step process that enables you to perform the migration without breaking your system.Let’s take a closer look at the backward-compatible operations first.The redundancy of all subsystems provides a lot of benefits.The two most important ones are: But they also create new challenges.That’s not the case for columns with a not null constraint because it will contain null values for all existing records.You can easily fix that by providing a default value; please check your database documentation on how to do that.
In that case, your operation is backward compatible, and you can simply add the column.No application is using that column anymore so there is also no application that could be affected by its removal.The removal of the constraint itself is a backward-compatible operation.A user who visits our site will be able to create posts that will be saved in a mysql database, retrieve the posts from the database and display them on the web page. The info table should have the following columns: I usually like to separate my HTML code from my PHP code as much as possible. On that note, let's create another file called php_where we implement all php functionalities like connecting to the database, query the database and the like. Each post will be displayed with an edit and delete button to permit the user to update posts as well as delete them. So open php_and paste the following code in it: At this point, all that this code does is connect to the database, initialize some variables and saves submitted data from the form to the database in the info we created earlier.