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Secured an interview for a role in SQL? Whether you’re interviewing for beginner or advanced SQL roles, here are some of the most common SQL interview questions an employer may ask, with example answers - so you’ll feel confident and prepared heading into any interview!
To gain an insight into the extent of your SQL knowledge, an employer may begin an interview by asking you what your experience with SQL is so far, along with general questions regarding the role.
Whilst employers will most likely have your CV in front of them, they want to hear you talk confidently about your previous experience and make a case for why you’re suited to their role, here are some general SQL questions an interviewer may ask.
When answering this question, you want to talk about the previous roles you’ve held where you’ve had experience using SQL. Be sure to include any programmes or software you know how to use and if you’ve undertaken any training courses or gained any qualifications. Tell an employer what you enjoyed about working in each of the roles, this will show you’re interested and passionate about the industry. It’s beneficial to also include if you’ve had any experience using other coding software, as this shows you’re a highly advanced coder and can translate a lot of your previous skills to this role.
The purpose of this question for the employer is to know if you’re serious and suited to their role. In your answer, you want to include why you’re interested in working in SQL, try to avoid generic answers, but include any particular reasons and aspects of SQL that really drive you. It’s also important to explain to the employer what you want to develop through their role, as this shows you have a willingness to learn and advance your SQL abilities.
Here’s a good example answer:
“I feel there can be a real sense of achievement working in SQL, from solving broken queries to designing new ones! There is so much to learn working with SQL, it’s an exciting and growing coding language and I want to expand my query design abilities through this role.”
If you’re interviewing for a junior SQL role, an employer won’t expect you to know how to perform advanced queries and know all the technical terms just yet, instead, they’ll want to know if you have a basic understanding of SQL.
“SQL (Structured Query Language) is a standard computer language for database management and manipulation. In database systems, statements are used to generate queries from a client program to the database, this allows a user to extract a wide range of fast data manipulation. The main functions of SQL are querying and editing information stored in a certain database management system, whether this is inserting, searching, updating or deleting database records.”
An employer may want to explore your knowledge of SQL further and ask why this coding language is important, you want to try and avoid generic answers, but delve deeper in your answer and give examples where you can. Here’s a good example answer:
“SQL is important for a number of reasons, one of these being that SQL has the capabilities to deal with large volumes of datasets stored in databases, that other systems couldn’t cope with. SQL is completely equipped to handle data pools of virtually all sizes. Almost every PC and mobile device will eventually require and touch with SQL as data rises to databases, they cannot function without SQL – making it a highly essential coding language. As companies strive to accomplish more with their information, SQL is key in allowing this to be achieved. SQL is a coding language that is relied upon by multiple databases around the world, making it an exciting industry to work in.”
If you’re interviewing for a slightly more experienced SQL role, employers may ask questions to explore the extent of your SQL query knowledge, here are some example SQL query interview questions and answers.
“PL/SQL is a Procedural language that holds SQL statements within its syntax. The basic difference is that in SQL a single query gets executed at a time whereas in PL/SQL a whole block of code can get executed at a time. Another key difference between SQL and PL/SQL is the way the two write, with SQL you can write queries and command using DDL and DML statements, whereas in PL/SQL you can write a block of code that has procedures, functions, and variables.”
“Joins in SQL are commands which are used to combine rows from two or more tables, based on a related column between those tables. They are mainly used when a user is trying to extract data from tables which have too many relationships between them. The main types of joins in SQL are Inner, Outer, Cross and Self joins.
“Indexes in SQL are special lookup tables that the database search engine can use to speed up data retrieval. An index helps to speed up SELECT queries and WHERE clauses. They have the same function as an index in the back of a book, they can be inserted or dropped to point to data, without having an effect on any of the data.”
If you’re interviewing for a SQL role related to SQL servers, an employer may ask questions to find out the extent of your SQL Server knowledge, here are some example SQL Server interview questions and answers.
“A SQL server profiler is a tool that helps developers trace, track and troubleshoot problems, giving them a high-level view of the operation of a system. Users create traces to capture data and then use the profiler to store, retrieve and view the results of those traces to repair and troubleshoot issues.”
“There are a few performance issues SQL servers face, some of these are poor queries, slow processing, memory pressure, excessive CPU usage.”
In your answer, show an employer your SQL knowledge is highly advanced, and list a few of the solutions to these issues.
“To troubleshoot a few of these issues, you want to ensure the TempDB database is configured optimally and make sure you’re running index maintenance frequently.”
When interviewing for SQL tester related roles, an employer will want to know the extent of your database testing knowledge and experience, when answering each question, you want to include any experience you’ve had with SQL testing along with examples and what you learnt from each experience. Here are some example SQL interview questions for testers with example answers.
“Database testing or back-end testing is checking the schema, tables, triggers of the database by creating complex queries to test the database and check its responsiveness. This type of testing chiefly deals with all the testable items that are generally hidden from the user for viewership. Database testing is highly important to ensure the values that an application is retrieving or storing into the database are accurate.”
“DBMS is a database management system, which is a software package designed to define, manipulate and retrieve data in a database. Some DBMS examples include MySQL, SQL Server, Oracle, FileMaker and Clipper.”
Interviewing for an advanced SQL role? Employers will often set tasks to see how advanced your knowledge is, here are some tips for how to handle SQL based tasks and example SQL interview questions for experienced professionals.
An interviewer will ask this question for multiple reasons, they want to know how advanced your SQL knowledge is, but also how you deal with difficult situations. You want to attend an interview prepared with an example of a SQL project you’ve previously worked on. In your answer include what you learnt from the project, what you enjoyed and what the main challenges were and how you overcame these.
To see how advanced your SQL abilities are, employers may set tasks for you to complete before an interview, often asking you to solve or write SQL queries. In an interview, an employer may want to discuss your task and understand your reasons behind your query design. It’s important to attend an interview prepared to talk through your work, spend a few hours before an interview going over your task and justifying your reasons behind making certain decisions.
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Whether you’re interviewing for a beginner or advanced SQL role, use our SQL interview questions and answers to prepare for your interviews and confidently showcase your knowledge of the industry and explain why you're suited to a company's role.
If you’re applying to graduate SQL roles, you need a standout graduate CV to attract an employer's attention and secure an interview, visit our CV Hub for CV templates, tips and examples! Find out some of the key skills required for graduate technology jobs.
Considering a graduate career in SQL? Discover our range of graduate IT, Software and Engineering jobs in London and the UK!