HPCL-Mittal Energy Limited Interview Questions and Answers

A Database Management System (DBMS) is a software that allows users to create, retrieve, update, and manage data in a database.

• DBMS helps in organizing and structuring data efficiently

• It provides tools for data manipulation, querying, and security

• Examples include MySQL, Oracle, SQL Server

A trigger function in SQL is a stored procedure that is automatically executed in response to certain events on a particular table.

• Triggers can be set to execute before or after INSERT, UPDATE, or DELETE operations on a table.

• They are useful for enforcing business rules, auditing changes, and maintaining data integrity.

• Example: CREATE TRIGGER audit_trigger AFTER INSERT ON employees FOR EACH ROW EXECUTE PROCEDURE audit_function();

SQL query for XYZ scenario

• Use SELECT statement to retrieve data from the table

• Use WHERE clause to filter data based on the XYZ scenario

• Consider using JOIN if data from multiple tables is needed

Hive is a data warehouse infrastructure built on top of Hadoop for providing data summarization, query, and analysis.

• Hive uses a SQL-like language called HiveQL to query and manage large datasets stored in Hadoop.

• It allows users to write complex queries without needing to know Java or MapReduce.

• Hive organizes data into tables, partitions, and buckets for efficient querying and analysis.

• It supports custom MapReduce scripts and UDFs for advanced data processing.

• Hive is commonly...read more

A primary key is a unique identifier for each record in a database table.

• A primary key must contain unique values for each record in the table.

• It cannot contain null values.

• It can consist of one or multiple columns.

• Example: In a table of students, the student ID can be a primary key.

Joins in SQL are used to combine rows from two or more tables based on a related column between them.

• Joins are used to retrieve data from multiple tables based on a related column between them

• Common types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN

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