Database History and DBMS Architecture Quiz

1. 1960s: Development of the hierarchical model by IBM. 2. 1970s: Introduction of the relational model by E.F. Codd. 3. 1980s: Emergence of the object-oriented database model. 4. 1990s: Introduction of the XML database model. 5. 2000s: Rise of NoSQL databases.

1. Online transaction processing (OLTP) systems. 2. Data warehousing and business intelligence. 3. Customer relationship management (CRM) systems. 4. Content management systems (CMS). 5. E-commerce applications. The most traditional DB application is online transaction processing (OLTP). OLTP systems have influenced DB technology by requiring high availability, concurrency control, and transaction management features in DBMSs.

The layered architecture of a DBMS consists of multiple levels of abstraction: 1. External Schema: Defines how individual users or applications view the data. 2. Conceptual Schema: Represents the overall logical structure of the entire database. 3. Internal Schema: Describes the physical storage structure of the database on the storage medium. These schemas correspond to different levels of the DBMS architecture, where the external schema is closest to the user/application, the conceptual schema provides a global view of the database, and the internal schema deals with the physical storage details.

Referential integrity constraint ensures that the relationships between tables in a database are maintained correctly. It is enforced through the use of keys, specifically primary keys and foreign keys. Here is an example with two tables, 'Customers' and 'Orders': - Customers table has 'CustomerID' as the primary key. - Orders table has 'OrderID' as the primary key and 'CustomerID' as a foreign key. When the referential integrity constraint is satisfied, each 'CustomerID' value in the Orders table must exist in the Customers table. For example, if the Customers table has a record with 'CustomerID' = 1, then the Orders table can have multiple records with 'CustomerID' = 1, indicating that those orders belong to the customer with 'CustomerID' = 1. If the referential integrity constraint is not satisfied, it means that there is a value in the foreign key column (e.g., 'CustomerID' in the Orders table) that does not exist in the referenced primary key column (e.g., 'CustomerID' in the Customers table).

An example of a DB operation that can lead to a problem with referential integrity is deleting a record from the referenced table (e.g., Customers table) without updating or deleting the corresponding records in the referencing table (e.g., Orders table). This can result in orphaned records in the referencing table, where the foreign key values no longer match any primary key values in the referenced table.

1. Reject the operation: The DBMS can choose to reject the operation that violates the referential integrity constraint, preventing any changes to the affected data.2. Cascade: The DBMS can automatically propagate the changes made to the referenced table (e.g., deleting a record) to the referencing table (e.g., deleting all corresponding records), ensuring that the referential integrity constraint is maintained.3. Set Null: The DBMS can set the foreign key values in the referencing table to NULL when the referenced record is deleted, indicating that the relationship no longer exists. This strategy allows for the deletion of records in the referenced table without violating the referential integrity constraint.

DBMS architecture = Explains the layered structure of database system Data Abstraction = Concept of hiding the details of how data is stored Three schemas in data abstraction = Relates to the architecture of a DB system environment Referential integrity constraint = A condition that requires a foreign key value to be matched with a primary key value in another table

Satisfying referential integrity constraint = DB operation is successful Not satisfying referential integrity constraint = DB operation leads to a problem DBMS rejecting operation = Occurs when referential integrity constraint is not satisfied Applying compensation strategy = DBMS's response when a problem occurs

Traditional DB application = Impacted the development of DB technology DB history milestones = Associated with respective decades DB applications = Significant developments in the field of databases Constraint satisfaction = Impacts the success of DB operations

Primary key = Uniquely identifies each record in a table Foreign key = Links two tables together Referential integrity constraint = Involves primary and foreign keys DB operation = Can lead to a problem if the referential integrity constraint is not satisfied

Compensation strategy = Applied when a problem occurs Referential integrity constraint = If not satisfied, leads to DB operation problem DBMS rejecting operation = Strategy when referential integrity constraint is not satisfied DB operation problem = Can be solved by rejecting operation or applying compensation strategy