What is the difference between SQL and NoSQL databases?

 Theme: Technical Skills  Role: Back End Developer  Function: Technology

  Interview Question for Back-End Developer:  See sample answers, motivations & red flags for this common interview question. About Back-End Developer: Manages server-side logic and databases for software applications. This role falls within the Technology function of a firm. See other interview questions & further information for this role here

 Sample Answer 


  Example response for question delving into Technical Skills with the key points that need to be covered in an effective response. Customize this to your own experience with concrete examples and evidence

  •  Definition: SQL (Structured Query Language) databases are relational databases that use tables to store and organize data. NoSQL (Not Only SQL) databases are non-relational databases that use various data models to store and organize data
  •  Data Structure: SQL databases use a predefined schema with a fixed structure, where data is stored in tables with rows and columns. NoSQL databases have a flexible schema, allowing for dynamic and unstructured data storage
  •  Scalability: SQL databases are vertically scalable, meaning they can handle increased load by upgrading the hardware. NoSQL databases are horizontally scalable, meaning they can handle increased load by adding more servers to distribute the data
  •  Query Language: SQL databases use SQL as the query language for retrieving and manipulating data. NoSQL databases use various query languages, such as document-based query language, key-value query language, or graph query language, depending on the data model
  •  Data Relationships: SQL databases are designed for structured data with predefined relationships between tables. NoSQL databases are suitable for unstructured or semi-structured data with flexible relationships
  •  ACID Compliance: SQL databases are ACID (Atomicity, Consistency, Isolation, Durability) compliant, ensuring data integrity and reliability. NoSQL databases may sacrifice ACID compliance for scalability and performance
  •  Use Cases: SQL databases are commonly used for applications with complex relationships and transactions, such as financial systems. NoSQL databases are suitable for applications with large amounts of unstructured data, real-time analytics, and high scalability requirements
  •  Examples: Examples of SQL databases include MySQL, Oracle, and PostgreSQL. Examples of NoSQL databases include MongoDB, Cassandra, and Redis

 Underlying Motivations 


  What the Interviewer is trying to find out about you and your experiences through this question

  •  Technical knowledge: Assessing the candidate's understanding of different database types and their characteristics
  •  Problem-solving skills: Evaluating the candidate's ability to identify and select the appropriate database type based on specific project requirements
  •  Adaptability: Determining if the candidate can work with different database technologies and adapt to changing project needs

 Potential Minefields 


  How to avoid some common minefields when answering this question in order to not raise any red flags

  •  Lack of understanding: Providing incorrect or vague definitions of SQL and NoSQL databases
  •  Superficial knowledge: Not being able to explain the key differences between SQL and NoSQL databases
  •  Inability to provide examples: Failing to provide specific examples of when to use SQL or NoSQL databases
  •  Lack of experience: Not being able to discuss personal experience or projects related to SQL or NoSQL databases
  •  Limited knowledge of use cases: Not understanding the typical use cases or advantages of SQL and NoSQL databases
  •  Inability to discuss scalability: Not being able to explain how SQL and NoSQL databases handle scalability differently
  •  Failure to mention data structure: Neglecting to mention that SQL databases use structured data while NoSQL databases can handle unstructured data
  •  Ignoring ACID properties: Not discussing the ACID (Atomicity, Consistency, Isolation, Durability) properties of SQL databases and how NoSQL databases may sacrifice some of these properties
  •  Lack of knowledge about query language: Not being familiar with SQL's standardized query language and the lack of a standardized query language in NoSQL databases
  •  Overgeneralization: Making broad statements about SQL or NoSQL databases without considering the various types and implementations within each category

 Related

  Other questions asked for the Back-End Developer in Technology function. View details for the Back-End Developer here