SQL has several simples to use commands for data processing activities. You can use SQL commands for the following purposes:
1. Creating, deleting, and modifying the table structure.
2. Defining the relationships between two or more tables.
3. Inserting data into tables.
4. Extracting data in meaningful ways, based on the tables defined relationships.
5. Updating data. This includes maintaining data in a database and manipulating the stored values to keep the information current.
6. Controlling a database. This includes system security and authorization which must be controlled and maintained.
Disadvantages of SQL:
1. SQL has a complex interface that creates difficulty for some user to access it.
2. SQL has a high operating cost.
3. Interfacing of SQL database is more complex than adding a few lines of code.