SQL

You can use an SQL question to test a candidate's knowledge of queries used to retrieve relevant data from a specific database. While creating a test, you can either use SQL questions from HackerEarth's in-built library or create your own questions. 

SQL problems help you assess the following skills:

• Conceptual knowledge of an SQL server
  A candidate must be able to understand the basics of Structured Query Language and be able to write and understand complex queries to retrieve data based on the requirements from the following databases:
  
  

  S. No.	Database	Version
  1	MySQL	8.0
  2	PostgreSQL	13.1
  3	SQL Server	2019
  4	Oracle Database	11g

• Program optimization skills
  Determine how a candidate writes a query with an ideal execution time. An efficient solution is one that takes the least amount of time for execution.

• Expertise in the basics of SQL
  Allows you to test and determine a candidate’s skills across basic SQL topics including, but not limited to, the following:
  • Advanced functions
  • Aggregate functions
  • Analytic functions
  • Arithmetic operations
  • Case statements
  • Date and time functions
  • Intersections
  • Joins
  • Multiple nested queries
  • Nested case statements
  • Nested queries
  • Numeric functions
  • Recursive functions
  • String operations
  • Unions
  • Relational operations
  • Window functions 

• Analytical and problem-solving abilities
  You can restrict the database that a candidate can use while writing queries. This allows you to assess how a candidate writes queries related to a specific database based on your requirements and real-time problems that you need solutions for.

• Hands-on experience in writing the SQL queries
  You can also determine if candidates are familiar with the SQL concepts including but not limited to the following:
  • Creation and implementation of databases
  • Maintenance and performance assurance of databases
  • Transaction control
  • Exception and error handling
  • Row processing
  • Declared variables