10+ Database Engineer Interview Questions and Answers

A database is a structured collection of data, Data Warehousing is the process of collecting and managing data from various sources, data lake is a storage repository that holds a vast amount of raw data, and datamarts are subsets of data warehouses.

• Database is a structured collection of data organized for easy access, retrieval, and management.

• Data Warehousing involves collecting and managing data from various sources to provide meaningful insights for decision-making.

• Data l...read more

Fill the 3L cup, pour it into the 5L cup, fill the 3L cup again, pour into the 5L cup until it's full, leaving 1L in the 3L cup.

• Fill the 3L cup

• Pour the water from the 3L cup into the 5L cup

• Fill the 3L cup again

• Pour the water from the 3L cup into the 5L cup until it's full, leaving 1L in the 3L cup

I have experience working with AWS, Azure, and Google Cloud Platform.

• Managed databases on AWS RDS and Aurora

• Implemented data pipelines on Azure Data Factory

• Utilized Google Cloud SQL for database management

CAP theorem states that in a distributed system, it is impossible to simultaneously guarantee consistency, availability, and partition tolerance.

• CAP theorem: Consistency, Availability, Partition tolerance - pick two

• Column families: A way to organize data in NoSQL databases like Apache Cassandra

• Functions in Cassandra: read, write, delete, update

• Key value pair: Basic data structure where each key is associated with a value

Different types of commands in SQL include Data Definition Language (DDL), Data Manipulation Language (DML), Data Control Language (DCL), and Transaction Control Language (TCL).

• DDL commands are used to define the structure of database objects such as CREATE, ALTER, DROP.

• DML commands are used to manipulate data in the database such as SELECT, INSERT, UPDATE, DELETE.

• DCL commands are used to control access to data in the database such as GRANT, REVOKE.

• TCL commands are used to ma...read more

Cassandra functions are used for data manipulation and retrieval in Cassandra database.

• Aggregate functions like COUNT, SUM, AVG, MIN, MAX

• Date and time functions like NOW, DATEOF, UNIXTIMESTAMP

• Mathematical functions like ABS, CEIL, FLOOR, SIN, COS

• String functions like LENGTH, SUBSTRING, CONCAT, LOWER, UPPER

Column families are a way to organize related data in a NoSQL database, grouping columns together for efficient retrieval.

• Column families are a way to group related columns together in a NoSQL database.

• They are used in databases like Apache Cassandra to organize data efficiently.

• Column families can contain a large number of columns, each with a unique name and value.

• They are stored together on disk for faster retrieval and processing.

• Column families allow for flexible schema ...read more

Key value pair is a data structure where each key is associated with a corresponding value.

• Key value pairs are commonly used in dictionaries, hash tables, and JSON objects.

• Keys are unique identifiers that are used to access the corresponding values.

• Examples include 'name: John', 'age: 30', 'city: New York'.

Union combines and removes duplicates, Union All combines without removing duplicates.

• Union combines result sets and removes duplicates

• Union All combines result sets without removing duplicates

• Union is slower than Union All as it involves removing duplicates

• Union All is faster than Union as it does not remove duplicates

Sharding and partitioning are both methods of dividing data across multiple servers, but sharding is typically used for horizontal scaling while partitioning is used for vertical scaling.

• Sharding involves splitting data horizontally across multiple servers, with each server handling a subset of the data.

• Partitioning involves splitting data vertically within a single server, with each partition handling a subset of the data.

• Sharding is typically used for large-scale distribute...read more

Cassandra is a distributed NoSQL database management system designed for handling large amounts of data across multiple servers.

• Cassandra is a highly scalable and fault-tolerant database system.

• It is based on a distributed architecture, with data spread across multiple nodes.

• Cassandra uses a masterless design, where all nodes are equal and can handle read and write requests.

• It uses a partitioning strategy called consistent hashing to distribute data evenly across nodes.

• Cassan...read more

Various types of joins in databases

• Inner Join: Returns rows when there is a match in both tables

• Left Join: Returns all rows from the left table and the matched rows from the right table

• Right Join: Returns all rows from the right table and the matched rows from the left table

• Full Outer Join: Returns rows when there is a match in either table

• Cross Join: Returns the Cartesian product of the two tables

MySQL is an open-source relational database management system known for its reliability and performance.

• MySQL uses structured query language (SQL) for database operations.

• It supports various storage engines like InnoDB and MyISAM.

• MySQL is widely used in web applications, such as WordPress and Joomla.

• It allows for ACID-compliant transactions, ensuring data integrity.

• MySQL can handle large databases, with support for millions of records.