SQL fundamentals
SQL is used to manipulate the data in the database and to query the database. Also, SQL is used to define the structure of the data. You already know that from the previous chapters. In general, SQL consists of three parts:
- Data Definition Language (DDL)
- Data Manipulation Language (DML)
- Data Control Language (DCL)
The first part is used to create and manage the structure of the data, the second part is used to manage the data itself, and the third part—to control access to the data. Usually, the data structure is defined only once and then it is rarely changed. But the data is constantly inserted into the database, changed or retrieved. For that reason, DML is used much more often than DDL.
SQL is not an imperative programming language, which makes it different from many other languages. To be more specific, one cannot define a detailed algorithm of how the data should be processed, and this might make an impression of lack of control of the data. In imperative languages...
