8.2 Database Management Systems (DBMS)

# Features of a DBMS:
- **Data management:** data stored in relational databases - tables stored in secondary storage
- **Data dictionary:** Stores metadata about the database including:
    - field / attribute names
    - table name
    - validation rules
    - data types
    - primary keys // foreign keys
    - relationships
- **Data modeling:** analysis of data objects used in database, identifying relationships among them
- **Logical schema:** A model of a database that is not specific to one DBMS:
    - the overview of a database structure
    - models the problem (situation) by using methods such as an ER diagram
    - independent of any particular DBMS
- **Data integrity:** Methods of making sure the data is consistent
    - Enforcing referential integrity
    - If data in one table is deleted/edited all tables are updated // cascading update/delete
    - Validation/verification rules
- **Data security:** handles password allocation and verification, backups database automatically, controls what certain user’s view by access rights of individuals or groups of users
    - **Access rights:**
        - give different people access to different elements by having different accounts which have different access rights e.g. read only // no access / read /write.
        - Specific views can be assigned to different people.
# Tools in a DBMS
- **Developer interface:** A software tool that allows the user to create items such as tables, forms and reports
- **Query processor:** Software that allows the user to enter criteria, then finds and returns the appropriate result(processes and executes queries written in SQL):
    1. allows the user to enter criteria
    2. searches for the data that meets the entered criteria
    3. organises the results to be displayed to the user