SCAS - BCA ANSWER SCHEMES

  Section A (2 marks each) 1. Compare Primary Key and Unique Key Feature Primary Key Unique Key Uniqueness Must be unique Must be unique Null Values Not allowed One NULL allowed Number per Table Only one Multiple allowed Purpose Ensures entity integrity Enforces uniqueness   2. DDL Commands in SQL Command Description Example CREATE Create tables or database objects CREATE TABLE Students(id INT, name VARCHAR(50)); ALTER Modify existing table ALTER TABLE Students ADD COLUMN age INT; DROP Delete table or object DROP TABLE Students; TRUNCATE Remove all records TRUNCATE TABLE Students;   ...