The power of the Power BI model comes primarily from a smart data storage mechanism. Power BI models are, in fact, databases in the sense that they organize and store data. But the internals are very different from other database technologies you may be familiar with.

Relational databases

The traditional, corporate way of working with data is with a relational database management system (RDBMS) like Microsoft SQL Server. In an RDBMS, tables of data are defined with a fixed number of data columns per table. Each column must have a data type, like integer, text, or decimal number, and from this information, the RDBMS can derive how much space is needed to store a single row of data, or record, and how many rows can be stored in a disk-based data file. This concept makes an RDBMS an effective choice for applications that process transactions, like sales transactions from a web shop or transactions in a company's financial ledger.

The concept of...