For now, the system should have 6 different user levels.
Each level will be gained upon user activity, for example:
Level 1 - When user register
Level 2 - When user completes a mission
Level 3 - When user completes more than one mission
Level 4 - When user donate > $X amount of money
Level 5 - When user write more than 50 comments in blog
Level 6 - When user complete quiz
And now... I'm wondering, what's the best database schema to achieve this? I should keep track of all actions related to user's activities, that's why I though about xp_events table... Something like this:
id # primary key
event # type of event, e.g. 'register', 'complete_quiz', etc.
user_id # id of user
delta # number of "exp" which will be gained after specific action
And... in users table I will keep record of current level and "exp" which each user has earned until now.
When user makes any activity, I will call a trigger which will check if user have new level unlocked.
But... I'm aware that in long term (e.g. if more levels are added), this isn't optimal solution.
Looking forward for any suggestions.
I see two obvious possibilities here.
One is to have an event table like you say, with a user ID, event ID, dollar amount (for donations), probably a date/time, maybe other data. If the only reason why you are keeping any of this data is to determine each user's level, this is simple and effective.
If you're keeping track of this data for other purposes also, you probably want to separate it into multiple tables. In such a case you would likely have other data you need to keep for each event. Like for a donation you would need dollar amounts, which I assume don't apply to comments and missions. For comments you likely need the text of the comment and some indication of the thread this comment is on or what it's subject is. For a mission -- I don't know what a "mission" is in this context, but you likely want some information about the type of mission and where it was or who they were supposed to kill or whatever. Most of this data would not be applicable to events of different types. A comment probably doesn't have a dollar amount, a mission doesn't have a thread, etc. So you'd end up with a lot of irrelevant data and bunches of null fields.