L2 Engineer Interview Questions and Answers for Freshers

No, primary keys should not be deleted as they uniquely identify each record in a database.

• Primary keys are essential for maintaining data integrity and ensuring uniqueness of records.

• Deleting a primary key can lead to data inconsistencies and errors in the database.

• If a primary key needs to be changed, it is better to update it rather than delete it.

Drop means to remove a database object, while delete means to remove data from a table.

• Drop is used to remove an entire database object like a table, view, or database itself.

• Delete is used to remove specific rows of data from a table.

• Drop operation is irreversible and can lead to loss of data, while delete operation can be rolled back if within a transaction.

• Example: DROP TABLE employees; DELETE FROM employees WHERE age > 50;

Triggers are special stored procedures in databases that are automatically executed or fired when certain events occur.

• Triggers are used to maintain data integrity by enforcing business rules or automating actions.

• They can be set to execute before or after an INSERT, UPDATE, or DELETE operation on a table.

• Examples of triggers include auditing changes to a table, updating a related table when a record is inserted, or enforcing constraints.