This lesson gives an introduction towards basic relational database management system concepts. It serves theoretical purpose only. You don’t need this in order to build an application. However understanding what your WordPress system is doing “under the hood” can help put other lessons in context.
A relational database system (DBS) consists of the following components:
What is the ACID concept?
For the database system to achieve all this, transactions are used. Transactions are a sequence of operations which result in different states of data. Those operations do not change data accessible by other users until a commit is sent to the DBS. Once a commit is done, only changed records can be accessed, no longer the ones before a change was made.
In order to deal with data in terms of a database system we have to distinguish between the following languages, which are part of the overall Structured Query Language (SQL):
We use DDL when we create tables, DML when we insert, update or delete table data and IQL when we select certain parts of the database.
A transaction commit can be initiated automatically after each SQL operation or manually using the commit command sent to the database. This is useful whenever you want to collectively change certain data bound together by a business case, without letting just portions of it being accessed by users.
For you as a blogger it is important to understand when database actions are performed and which category they belong to:
The last point already shows why you as both blogger and WordPress administrator will most likely use caching plugins. Those will pre-load all needed database contents and created static HTML to be served to the browser on each request. That way we prevent the whole database requesting (IQL) processes from being being repeated over and over again for each request without actually having new content in the database. Those plugins have to rebuild that static HTML only when you change a posts content.