[Q.21] In SQL, which command is used to permanently remove a table and its structure from a database?
DROP removes table structure and data permanently.
[Q.22] A Foreign Key in a relational table establishes:
Foreign key enforces referential integrity to primary key of another table.
[Q.23] Which Normal Form eliminates partial functional dependencies (where a non-key attribute depends on part of a composite primary key)?
2NF requires 1NF and no partial dependencies on composite keys.
[Q.24] Which ACID property ensures that all operations in a database transaction complete successfully or none are applied?
Atomicity guarantees 'all or nothing' transaction execution.
[Q.25] In relational algebra, which operator is represented by the Greek symbol Sigma (sigma)?
Sigma represents Selection (row filtering) in relational algebra.