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23 Databases interview questions and answers for software engineers

A database is an organized collection of data, generally stored and accessed electronically from a computer system. Where databases are more complex they are often developed using formal design and modeling techniques. Here is a list of coding interview questions on Databases to help you get ready for your next data structures interview in 2021.

  • 1.

    What is Normalization?

    Answer:

    It is the process of eliminating redundant data and maintaining data dependencies.

    Source: github.com/dhaval1406   
  • 2.

    What are the advantages of NoSQL over traditional RDBMS?

    Answer:

    NoSQL is better than RDBMS because of the following reasons/properities of NoSQL:

    • It supports semi-structured data and volatile data
    • It does not have schema
    • Read/Write throughput is very high
    • Horizontal scalability can be achieved easily
    • Will support Bigdata in volumes of Terra Bytes & Peta Bytes
    • Provides good support for Analytic tools on top of Bigdata
    • Can be hosted in cheaper hardware machines
    • In-memory caching option is available to increase the performance of queries
    • Faster development life cycles for developers

    Still, RDBMS is better than NoSQL for the following reasons/properties of RDBMS:

    • Transactions with ACID properties - Atomicity, Consistency, Isolation & Durability
    • Adherence to Strong Schema of data being written/read
    • Real time query management ( in case of data size < 10 Tera bytes )
    • Execution of complex queries involving join & group by clauses
    Source: stackoverflow.com   
  • 3.

    Define ACID Properties

    Answer:

    • Atomicity: It ensures all-or-none rule for database modifications.
    • Consistency: Data values are consistent across the database.
    • Isolation: Two transactions are said to be independent of one another.
    • Durability: Data is not lost even at the time of server failure.
  • 4.

    What is Denormalization?

    Answer:

    It is the process of improving the performance of the database by adding redundant data.

    Source: github.com/dhaval1406   
  • 5.

    What are the difference between clustered and a non-clustered index?

    Answer:

    • A clustered index is a special type of index that reorders the way records in the table are physically stored. Therefore table can have only one clustered index. The leaf nodes of a clustered index contain the data pages.
    • A non clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on disk. The leaf node of a non clustered index does not consist of the data pages. Instead, the leaf nodes contain index rows.
    Source: github.com/dhaval1406   
  • 6.

    How a database index can help performance?

    Answer:

    The whole point of having an index is to speed up search queries by essentially cutting down the number of records/rows in a table that need to be examined. An index is a data structure (most commonly a B- tree) that stores the values for a specific column in a table.

    Source: stackoverflow.com   
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