13 Database Programmer Interview Questions and Answers

Structured query language, or SQL, is a domain-specific programming language that works in a relational database management system or stream. SQL is the fundamental building block of the database industry, and you need to know that a new contractor is proficient. It can use aggregate functions, order database objects by different values, and generate result sets. 

This is a fundamental question to start an interview. A database stores data with rows and columns using a database management system (DBMS). A data structure, on the other hand, exists only to access and alter data.

Many database management systems (DBMSs) are available, including MySQL, Oracle, and Microsoft Excel. Asking this question will help you get on the same page with a new team member as soon as possible. 

Anyone you contract to manage a database must understand its structure. This can lead down a lot of different paths. Still, depending on your project or organization, they should at least be able to explain the difference between relational database management systems (RDBMS) and non-relational database management systems (NRDMS). 

This is a technical question that addresses a fundamental part of a database structure. Asking this will give you some insight into how deep your contractor has dived into data science. The foreign key especially shows how the contractor may have worked with integrated or child tables and how well they maintained referential integrity.

This is a technical question you can ask to determine how your database specialist deals with redundant data. Sometimes this comes with adding data to a set, but that redundancy comes at a cost. A new contractor should be able to tell you both the function of normalization and denormalization and the benefits of using one over the other. 

Data definition language, or DDL, consists of commands that allow programmers to modify tables using create, select, and insert commands. This may lead the interviewee to start explaining the difference between SQL language and data definition language. 

This is a technical question that deals with the syntax of programming languages. One of these will result in the deletion of rows from a table and be committed or rolled back, while the other is permanent and cannot use the rollback function. Knowing that your interviewee understands the difference between these two commands can give you peace of mind in the future.

This is a method of joining SQL servers, and it is helpful to ask if you are looking to see how the interviewee can combine data from different sources. Someone who has this experience should be able to give you the four types of joins: full join, left join, right join, and full outer join and explain when they would use each one. 

The first part of this question sound like it’s from a quiz show and they’ll likely recite: unique index, clustered index, non-clustered index, but giving them a chance to think about the types of projects and implementations that they could possibly use them for is a bit of a fun strategic thinking exercise. 

If you already have a data team available to code a spreadsheet, you can ask your freelancer to do a technical question or two. This one can be used to calculate a date as long as there’s some sort of date in your data set. For example, list some employees and then add their date of joining. This will give you insight not only into how they think but how well they know the program.

This SQL interview question can show you how well your contractor knows different subsets of SQL commands and how well they can manage table security. DML deals with specific subsets of the language set into schema and includes SQL commands like delete, select, insert, and update. DCL deals specifically with controlling access to the data with grant and revoke commands.

ACID is a common acronym in the database world for atomicity, consistency, isolation, and durability. A strong database needs all these present, and hearing an anecdote about it will help you see how your interviewee troubleshoots.