Update and alter are two terms, which are generally often mixed up with one another. This tends to lead to people getting rather confused as to what it is that is going on, and just what it is that is actually happening. Update and alter are generally two words, which can be better understood when looking at them from the point of view of a database. Update can simply mean updating the existing records, while alter means that you go on and alter the records. This can be done by deletion, addition of fields that didn’t exist, or formatting and editing fields in the database.
So basically, update is a term which is used when you update existing records. This means that you go on and add new information, without you actually editing the original database. Most of the time, you simply add new data into the existing fields, or add new figures which come in as time goes by. Staying up to date, also means that you have to constantly add new information, as it is revealed to you, since having the latest and most up to date information is very important when it comes to databases and just about anything else, which is information based.
Altering things on the other hand, is when you actually take the existing data and edit it. This means that you modify the existing data by adding new information, deleting other things, or completely restructuring it. You aren’t actually putting in new information. Instead, you are just tweaking all the data that you actually have with you, and are looking to see how it can be arranged to optimize performances and the impact that it has on things.
So the main difference that you could say, is that when you update information, you are adding new information which has just come in and didn’t exist before. On the other hand, when you alter something, you are just editing the existing data, based on how you feel you can better utilize it.