Practice SQL Questions and Answers

• What is the primary purpose of a `SEQUENCE` in SQL?
• Which of the following statements about SQL `INDEXES` is generally TRUE?
• What is an SQL `VIEW`?
• What is the primary purpose of a `SEQUENCE` in SQL?
• Which of the following statements about SQL `INDEXES` is generally TRUE?
• What is an SQL `VIEW`?
• Which type of index physically reorders the data rows in the table itself based on the index key, meaning the data is stored in the order of the index?
• Which of the following is a key characteristic that distinguishes a PL/SQL `FUNCTION` from a PL/SQL `PROCEDURE`?
• In PL/SQL, what type of parameter allows a procedure to both receive a value from the calling environment and return a modified value back to it?
• Which of the following is a mandatory component of a PL/SQL function's definition?
• What is the primary purpose of a PL/SQL `CURSOR`?
• What is the correct sequence of operations for using an explicit PL/SQL cursor?
• Which PL/SQL cursor attribute returns `TRUE` if the most recent `FETCH` statement returned a row, and `FALSE` otherwise?
• When does an implicit cursor get automatically declared and managed by PL/SQL?
• What is the main function of a PL/SQL `TRIGGER`?
• Which type of index physically reorders the data rows in the table itself based on the index key, meaning the data is stored in the order of the index?
• Which of the following is a key characteristic that distinguishes a PL/SQL `FUNCTION` from a PL/SQL `PROCEDURE`?
• In PL/SQL, what type of parameter allows a procedure to both receive a value from the calling environment and return a modified value back to it?
• A `BEFORE INSERT` trigger fires:
• Which type of trigger fires once for each row affected by the triggering DML statement?
• Which of the following is a common use case for a PL/SQL trigger?
• Which of the following is not a type of SQL JOIN?
• What is the difference between DELETE, TRUNCATE, and DROP commands in SQL?
• In SQL, what is the difference between 'WHERE' and 'HAVING' clauses?
• In database management, which SQL command is used to retrieve only unique (non-duplicate) values from a column?
• What will be the output of the following SQL query? SELECT COUNT(*) FROM Transactions WHERE Amount > 10000 AND Status = 'Completed';
• What is a 'stored procedure' in SQL?
• Which query returns departments whose average salary is greater than 60000?
• Which SQL expression correctly returns employees whose salary is greater than the average salary of all employees?
• Orders(OrderID, CustomerID, Amount) has multiple orders per customer. Which query returns customers whose total order amount exceeds 100000?
• Table T has five rows and X values (10,20,NULL,20,NULL). What does SELECT COUNT(X) FROM T return?
• Given Employee(EmpID, Name, Salary, ManagerID), which query correctly lists employees who earn more than their own manager?
• Table B contains a NULL value in its 'id' column. Consider: SELECT * FROM A WHERE A.id NOT IN (SELECT id FROM B). What happens?
• A table has salaries 90000, 90000, 85000, 80000 (sorted descending). Using RANK() OVER (ORDER BY Salary DESC), what ranks are assigned, and how does this d...
• A table has a B-tree index on the 'Name' column. Which of the following queries is LEAST likely to benefit from this index?
• Transaction T1 runs 'SELECT COUNT(*) FROM Orders WHERE Amount > 1000' twice within the same transaction. Between the two reads, T2 inserts a new qualifying...
• Employees(emp_id, name, salary, mgr_id): (1,'Alice',9000,NULL), (2,'Bob',7000,1), (3,'Carol',9500,1), (4,'Dave',6000,2). What does the following self-join ...
• Customers(cust_id,name): (1,'A'),(2,'B'),(3,'C'). Orders(order_id,cust_id,amount): (1,1,200),(2,2,150),(3,1,300),(4,3,100). What does the following query r...
• Employees and salaries: Alice=9000, Bob=7000, Carol=9500, Dave=7000. What rank does Dave receive from the following query? SELECT name, salary, RANK() OVER...
• Table T(A,B) contains: (1,NULL), (NULL,2), (3,4), (NULL,NULL). How many rows are returned by the following query? SELECT * FROM T WHERE A=3 OR B=4;