TKIL Interview Questions and Answers

Query to fetch details of employees in the same department

• Use SELECT statement to fetch employee details

• Use JOIN to join employee and department tables

• Use WHERE clause to filter employees in the same department

Delete command removes rows one by one while truncate command removes all rows at once.

• Delete is a DML command while truncate is a DDL command.

• Delete can be rolled back while truncate cannot be rolled back.

• Delete command fires triggers for each row deleted, while truncate does not.

• Delete command is slower as it maintains logs for each row deleted, while truncate is faster as it does not maintain logs.

• Delete command can have a WHERE clause to specify which rows to delete, whil...read more

WHERE clause filters rows before grouping, HAVING clause filters groups after grouping.

• WHERE clause is used to filter rows based on a condition

• HAVING clause is used to filter groups based on a condition

• WHERE clause is used before GROUP BY clause

• HAVING clause is used after GROUP BY clause

• WHERE clause cannot contain aggregate functions

• HAVING clause can contain aggregate functions

• Example: SELECT department, AVG(salary) FROM employees WHERE age > 30 GROUP BY department HAVING AVG...read more

Use SQL query with GROUP BY and HAVING clause to delete duplicate records in a table.

• Identify the columns that define a duplicate record

• Write a SQL query to select the duplicate records using GROUP BY and HAVING clause

• Delete the duplicate records using DELETE statement with the identified criteria

OOPs is a programming paradigm that uses objects to represent real-world entities and provides encapsulation, inheritance, and polymorphism.

• Encapsulation: Hides the implementation details of an object from the outside world

• Inheritance: Allows creating a new class from an existing class

• Polymorphism: Allows objects of different classes to be treated as if they are of the same class

• Advantages: Reusability, Modularity, Flexibility, Maintainability

• Example: A car can be represented...read more

To join two tables with inner join, use the JOIN keyword along with the ON clause to specify the join condition.

• Use the JOIN keyword to combine rows from two tables based on a related column between them

• Specify the join condition using the ON keyword followed by the columns to join on

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column