Practice SQL Questions and Answers

• Which of the following is true about a foreign key?
• In normalization, which normal form removes transitive dependencies?
• Deadlock in DBMS can be prevented using:
• Which SQL keyword is used to eliminate duplicate rows in a query result?
• Which SQL function is used to calculate the average of a numeric column?
• Which SQL clause is used to filter results after a GROUP BY operation?
• Which SQL statement combines the results of two queries and removes duplicates?
• Which SQL function returns the largest value in a column?
• Which SQL command is used to modify existing records in a table?
• Which clause is used to sort query results in SQL?
• Which SQL operator is used to search for a pattern in a column?
• Which SQL keyword is used to remove duplicate records from a query result?
• Which SQL clause is used to filter records based on aggregate functions?
• Which operator is used to combine results of two SELECT queries and remove duplicates?
• SQL Injection can be prevented by all EXCEPT:
• Which SQL clause is used to filter groups after aggregation (i.e., having aggregated value conditions)?
• Given a table employees(id, dept_id, salary), which query returns departments with average salary greater than overall average across the company?
• Which of the following SQL constructs avoids returning duplicate rows?
• Which join returns rows from the left table even when there is no matching row in the right table, filling with NULLs for the right side?
• Which index type is most beneficial for queries that use range predicates (e.g., WHERE age BETWEEN 20 AND 30)?
• 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?