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SQL Foundations



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Posted on Tuesday, July 12, 2022

You invest a lot of valuable time, effort, and consideration when hiring an employee, and want to ensure that the candidate is the best fit for the position and the company. For job positions that mandate a specific skill set, such as SQL, make sure that your new hire has the knowledge and the expertise that the job requires.

SQL, Structured Query Language, is a common computer programming language for running queries in database systems and is used in many computer and technology fields. Some positions require just a familiarity with the language, and others may need the employee to be fluent in SQL on a specific database engine.

Job applicants may put SQL down on their resume as one of their skills, but they may not be proficient enough for the position. A senior developer, for example, needs to know more than just how to run a simple select statement. Recent college graduates may have learned about databases but may never have used SQL in practice.

What is the best way to measure a job candidate’s knowledge of SQL to determine whether they are the right fit for the job? Test all applicants on their SQL proficiency with a SQL test to confirm they can perform at the level the job requires.

How to Use SQL Tests in the Hiring Process?

Many job positions in the technology field require SQL, including computer programmers, software developers, data analysts, database managers, and information technology specialists.

To facilitate the interview process and ensure that the candidate you hire is as experienced as they claim, include a SQL test as part of the interview process. The SQL can include a preliminary verbal questionnaire to assess the applicant’s experience in using SQL, but should also include a hands-on technical test to evaluate their skills.

Benefits of SQL Tests for Hiring

By administering a SQL test before hiring a candidate, you’ll be able to assess their skill level and knowledge and determine whether they are qualified to do the job.

  • By knowing an applicant's SQL proficiency before hiring them, you can mitigate the risk of hiring an unqualified candidate for the job. Hiring and training new employees is very time-consuming and expensive, and you want to get the right hire the first time around.
  • Many entry-level applicants may not have enough SQL experience for positions where advanced SQL knowledge is necessary.
  • The SQL test will also help shorten the interview stage. You may find you can eliminate a percentage of the applicants based on the results of their SQL test. By giving the SQL test before the interview, you can save a lot of time on interviewing unqualified applicants.
  • The SQL technical test results give an insight into how the applicant codes and their line of reasoning. With the right questions, you can gauge how efficiently they use SQL. Did they use the syntax correctly? Are their statements optimized?

How to Assess and Use SQL Tests for Hiring?

As each position may require different levels and skill sets of SQL, you can customize the SQL tests to each role. Hiring managers may give different tests for different job positions. A software developer may need a higher level of SQL proficiency than an IT technical support representative.

It also helps to know whether the position requires knowledge and experience on a specific database engine. Many RDBMS, relational database management systems, use SQL. Know which one the company is using to ensure the new hires are familiar with them.

Popular RDBMS include Oracle, MYSQL, Microsoft SQL Server, SQLite, BM DB2, and PostgreSQL. Give the appropriate test based on the database that will be used, if it's applicable.

SQL Test Topics

SQL tests for hiring questions can cover a range of topics on various skill levels, from writing simple queries to more complex functions. The following are some examples of topics that your SQL tests might cover, depending on the job requirements.

  • Queries - commands to retrieve data from the database
  • Data manipulation - modify data in the database, including editing data, removing information, and inserting new rows
  • Database management - maintain and upkeep the structure of the database.
  • Data modeling - designing the structure of the database
  • Indexing - speeds up running queries and returning data
  • Constraints - conditions the data in the tables need to follow
  • XML data - uses unicode characters
  • Conditional filters - filter queries using the Where statement to return specific rows
  • JOIN statements - combine data from multiple tables to better evaluate the information
  • Sub-queries and nested queries - return data from more than one table into the results
  • Backups - database administrators will need to know how to backup and restore the databases
  • Optimization - running queries as efficiently as possible
  • Table-valued functions
  • Refactoring
  • Relational and transactional databases
  • Storage area network.

The pre-hiring SQL test may also cover some or all of the different types of SQL commands.

  • Data Definition Language (DDL) - statements that change the database structure, such as inserting new columns.
  • Data Manipulation Language (DML) - statements that modify the data in the database tables, such as adding rows or editing values.
  • Data Control Language (DCL) - statements managing what users can access on the database.
  • Data Query Language (DQL) - SQL statements that return information

Sample SQL Multiple Choice Questions

A multiple-choice question style test is an easy way to gauge an applicant’s SQL knowledge. Questions can range from proper syntax and language use to case scenarios.

  • What is a Relational Database Management System?
  • Which command would you use to remove a row from the table EMPLOYEES?
  • Which of the following statements will sort the results in descending order?
  • When would you use a wildcard in a WHERE statement?
  • How would you use the Group By clause?
  • Which of the following is not a major SQL constraint?
  • What is a non-clustered index?
  • Would you use a blank value, zero, or null in the following query statement?
  • Which statement will insert dates into the database?
  • What’s a Primary Key constraint?
  • What do the following functions do: Ucase(), Lcase(), Mid(), Format(), Len(), Round(), Avg(), Count(), Max(), Min(), Sum(), First(), Last()

Sample SQL Coding Test Questions

A coding test will assess the applicant’s SQL proficiency by having them type the SQL statements and run actual queries.

The following examples are a sampling of questions in the SQL test for hiring process. They can be modified and customized to suit the job position’s requirements.

  • For the following example, write a SQL statement that returns a list of employees whose last names begin with the letter S.

TABLE Employees

Id Integer Primary Key,

EmpFirstName varchar (50) Not Null,

EmpLastName varchar (50) Not Null

  • Return a list of Distinct employee last names beginning with S.
  • Return a list of all the employees’ names ordered in descending order.
  • Write an insert statement to add employee Jimmy Polk to the database.
  • Write an update statement to change the first name of Jimmy Polk to James.
  • Alter the table to add a column for the employees’ middle names.
  • Correct the syntax in a SQL query.
  • Create a new table called JOBS with a column for job descriptions.
  • Join the Employee table with the Jobs table.
  • Create a view using fields from multiple tables.

Advanced SQL Coding Tests

When interviewing senior programmers and software developers, a more advanced assessment of their SQL knowledge is necessary.

SQL tests for hiring programmers may involve data modeling, designing new tables, creating indexes, writing stored procedures, multiple-line sub-queries, normalizing database tables, implementing triggers to automate the database and more.

Programmers and developers in addition to knowing the syntax of SQL, will also need to have critical thinking skills, identify errors, and optimize the code to work most efficiently. Sometimes the syntax may achieve the right results, but the method employed is slow and cumbersome.

Their SQL test may also include an evaluation of the efficiency of their SQL statements, as well as the execution speed.

Recruiting for SQL

Programmers, developers, and database administrators all use SQL for their jobs. Their proficiency in SQL is crucial and isn’t something a recruiter can assess from an applicant’s resume or education. A SQL test is the best method to measure a job applicant’s SQL knowledge.

Recruiters need to know what level of experience in SQL the candidates need to have for each position.

Programmers and developers need to know how to write queries and stored procedures and manipulate data in the database.

Database administrators need to know how to maintain and optimize the SQL database.

Evaluate Skills

Before the technical SQL test, interviewers may find an oral soft-skill test to be beneficial in evaluating the applicants. These tests may cover situational questions that invite the applicant to expound upon their experience.

Questions may include how the applicant adapted to learning new programming languages, how they approach testing their work, and how comfortable they are working in teams.

SQL Test: Consideration for Recruiters

Before interviewing or testing candidates on SQL, determine the skill level the position requires. It’s best to have different levels of tests for varying levels of SQL knowledge needed. You may have a basic SQL test for entry-level positions, a standard SQL test for a moderate level of SQL knowledge, and an advanced SQL test for senior developers and programmers.

Evaluating SQL Test Results

The results of the SQL verbal assessment, multiple-choice questions, and technical coding test will give the recruiters a clear picture of the applicants’ SQL knowledge and skill.

  • Overall Score - The overall score will give a general view of how well the candidate knows SQL, both in practical working knowledge, and its concepts and usage.

For candidates who aren’t up to par on their SQL, but meet all of the other job requirements, they may be able to learn on the job, if the company is willing and has the resources to train.

SQL is an easy-to-learn language. If a job doesn’t require heavy SQL usage, and the company has the time and resources to train the new employees, a candidate without much SQL knowledge may do well.

For positions that use SQL heavily in their everyday roles, look for a candidate who expressed knowledge, proficiency, and skill in both the technical SQL test and during the assessment.

  • Subject Score - Break down the score by subject to evaluate how well the candidate knows the different areas of SQL. A candidate may have done well on the multiple-choice questions, but poorly on executing the SQL statements on the technical part of the test.
  • Ranking - Compare the test results of the candidate to other applicants to see how well they did in comparison. The percentile rating may help to select the right candidate.
  • Time Limit - If the SQL test was a timed test with a deadline, evaluate how long the candidate took to complete the exam. It may or may not play a factor in your hiring process. A fast test with a low score may indicate carelessness if the applicant hurried to complete the exam and sacrificed accuracy for speed.

Consider all factors before choosing the candidate to fill the SQL position. Each position requires many different qualities, and the highest SQL test score may not always be the right choice for the company or the job position.

For many jobs in the technology sector, employees need to be able to work both independently as a member of a team, accept constructive criticism, work well under pressure, employ creative thinking and logic, and have good work ethics. Add in exceptional SQL skills, and hopefully, you have found your new employee.