SQL Developer Interview Questions

sql developer interview questions

The age of file cabinets, paper documents, and folders is all but gone. Nearly all of today’s data and company information is maintained through databases that require systems to access and comprehend. 

In order to ensure that data is held reliably, easily accessible, and secure, we need a language to help us interact with and communicate with our databases. That’s where your SQL developer comes into the picture. 

What does a SQL developer do? 

SQL developers design, maintain, and analyze applications that interact with SQL database languages. These individuals usually have a strong IT background and are familiar with the ins and outs of SQL, app development, and database technology. 

Below are some SQL developer roles and responsibilities:

  • Developing SQL databases
  • Writing applications to interface with SQL databases
  • Working with project managers and business leaders to build databases and validate system requirements
  • Writing and testing code
  • Constructing tables, views, and functions
  • Improving application performances
  • Managing memory of database systems
  • Authenticating and authorizing databases

Common SQL interview questions

While SQL developers will be required to work with project managers and other team leaders, much of their work will be done alone on their computers, maintaining systems and databases as needed. You want to make sure this person has enough experience and technical knowledge of SQL development to meet their tasks on their own.

Here are some common questions to assess their overall knowledge of SQL technology.

  • What is SQL?
  • What are some basic SQL queries?
  • What are tables and fields?
  • How do businesses utilize SQL?
  • Why is SQL important to our company?
  • What is a primary key and unique key?
  • What is a join? Explain the various types of join.
  • What’s the largest database you’ve ever maintained?
  • You might need to work with other app developers in maintaining our databases. How well do you work with others?
  • What is an index?

SQL scenario interview questions

In order to really test an applicant’s understanding and ability to work with SQL, you can present some real-time scenario interview questions. This will give your candidate a chance to show their mastery of SQL development under pressure. Below are some SQL scenario question examples, provided by SQL World, which you can rely on to ensure your candidate has the technical ability and experience to take on both simple and complex SQL questions. 

Scenario #1: Ask your candidate how to find the second highest salary for employees with the below queries. 

  • Query 1: “Select distinct Salary from Employee e1 where 2=Select count(distinct Salary) from Employee e2 where e1.salary<=e2.salary;” (SQL World).
  • Query 2: “Select min(salary)from(select distinct salary from emp order by salary desc)where rownum<=2;” (SQL World).
  • “Query 3: Select * from(Select S.*,DENSE_RANK() OVER (PARTITION BY DNO ORDER BY SALARY DESC) DR from Source) S Where S.DR=2;” (SQL WORLD).

Scenario #2: Ask your candidate to find the Nth records from the table below. 

  • “Query 1 :  Query to find First Record from the table.

 Select * from Employee where Rownum =1;” (SQL World).

  • Query 2: Query to find last record from the table.

Select * from Employee where Rowid= select max(Rowid) from Employee; (SQL World).

  • Query 3 : Query to find Nth Record from the table. 

Select * from ( select a.*, rownum rnum from ( YOUR_QUERY_GOES_HERE — including the order by ) a where rownum <= N_ROWS ) where rnum >= N_ROWS; (SQL World).

A comprehensive list of similar SQL scenario interview questions can be found here

SQL server database architect interview questions

An SQL database architect supports, designs, and builds the systems that will store and retrieve data for your various processing and analytic needs. Especially if you’re working with several other software applications, you need to ensure that your SQL architect is well-versed with managing SQL servers so that you can retrieve and store data between applications. 

Much like the other aspects of an SQL interview, most of your questions will involve testing the applicant’s technical knowledge of SQL systems and SQL architect responsibilities. 

  • What steps will an SQL developer take to secure SQL servers?
  • What are the benefits of filegroups?
  • What’s the largest server you’ve worked on as a developer?
  • Define pages and extents
  • What is database architecture?
  • What are your first steps if an SQL server isn’t responding?
  • What are database objects?
  • What does a physical database architecture describe?
  • Define temp Db database

SQL BI interview questions

SQL server Business Intelligence describes a set of tools used for turning raw data into comprehensible information that businesses can utilize. SQL BI applications provide businesses with valuable insights and analytics into the nuances of their data. 

It’s important for your developer to demonstrate their familiarity with BI applications so that your leaders and team members can interact with, comprehend, and utilize the raw data that make up your various systems. 

  • Why is SQL BI important for a business?
  • What are the tools that BI consists of?
  • What recent projects help reflect your technical skill and knowledge of SQL BI?
  • How will BI help our business view our data?
  • What kind of analytics does SQL BI provide?
  • What are some workflow applications of SQL BI?
  • How will BI applications help our company?
  • How do you plan on keeping up with the trends and innovations in BI?

Final thoughts: Screening for an SQL Developer

The most important things to look for in an SQL developer candidate are their technical abilities and their previous experience. Utilize these exercise and interview questions to evaluate their capabilities as SQL developer with simple and complex SQL scenarios, assess their previous projects, and verify that your candidates can handle the scale of your business. 

>>>>To learn more about how to activate the Codility + Lever integration, check our ecosystem page for more details to screen and hire your next great SQL Developer! Or download our Definitive Guide: 101+ Interview Questions to Hire Faster for more ideas on great questions to ask during the screening process.