SQL Test

SQL Test

This page is about the Alooba SQL test. SQL is the single most commonly used skill, right across the spectrum of analytics roles, including data analyst, data engineer, data scientist, product analyst, marketing analyst & business intelligence analyst.

SQL is the most popular skill to assess using Alooba. It’s one of more than 40+ skills related to data & analytics that you can assess on Alooba. You can assess SQL in various ways on Alooba, including through the dedicated SQL coding environment and also the Concepts & Knowledge test type.

Here’s a free practice SQL test. Candidates can take this to gain practice before taking a real test for a job. Hiring managers can check out this free practice test to get a glimpse into how the test works.

Here’s a short explainer video, showing you how the SQL test works. This gives you a quick walkthrough of the SQL IDE and a few of the highlights.

You can also find some SQL concepts questions in the free data engineering test and the free data analyst test, for example.

Alooba SQL Test General FAQ

What is SQL?

SQL (pronounced either ‘S-Q-L’ or ‘see-quel’) stands for Structured Query Language. Long story short, it’s the language that’s used to interact with relational databases. Relational databases store data in tables, which consist of rows and columns. For simplicity, you could think of a relational database as like an Excel spreadsheet, where each tab of the spreadsheet is a table.

To be able to interact with the database programmatically, you use the language SQL.

People tend to think that computing and data science are relatively new, but SQL is nearly 50 years old, having been developed in the early 1970s at IBM in the United States.

Virtually every company in the world stores some of their crucial data in relational databases, and so SQL is an essential skill now, and is not likely to go away any time soon.

What are the different types of SQL?

Each version of SQL is subtly different. Basically, different companies have created their own database management systems, and with that, they have created proprietary versions of the original SQL.

All of these are based on ANSI-SQL and must comply with these ISO standards. Microsoft SQL Server (T-SQL), Redshift, MySQL, PostgreSQL, Snowflake, Oracle and Google Big Query are the most commonly used relational database management systems.

The SQL versions used in each of these systems are all very similar to each other. If you know any version of SQL, you can use all of them, with some minor initial adjustments. For example, in T-SQL, you use the keyword top instead of limit to return a specific number of rows. Once you make your way around a few of these minor syntactical differences, you’ll realize they’re much of a muchness.

The different versions of SQL are really like different versions of English. Whether you’re speaking Canadian-English or New Zealand-English, it’s all the same language.

What is an example of a SQL query?

SQL is actually quite a readable language. Let’s take a look at a quick example. Suppose you have a table of data called users, where 1 row represents 1 user for your product. In databases, a row is also called a record.

The users table will have various pieces of information that describe a user. For example, you might have the users’ first_name, last_name and email_address. And remember, a table is basically just like a spreadsheet, so all these dimensions are just columns.

Let’s suppose that your marketing team would like to send an email campaign, welcoming all the users who signed up using the coupon code ‘Alooba’.

They’d like this list, in order of when the user signed up, in reverse chronological order (most recent records appear first). Here’s what the query would look like:

SELECT    first_name, last_name, email_address
FROM      users
WHERE     coupon_code = ‘Alooba’
ORDER BY  created_at DESC
  • SELECT is used to choose which columns of data you want.
  • FROM is used to choose which table you want to get data from.
  • WHERE is used to filter the dataset to only the rows that you are interested in.
  • ORDER BY is used to arrange the dataset.
  • DESC stands for descending, and this basically means the data is ordered from highest to lowest.

It’s customary to put the keywords in UPPER CASE, but actually it doesn’t matter - SQL is case insensitive.

That’s just a quick example to give you the idea about SQL. Fairly readable, right?

What’s the difference between DML, DDL and DQL?

DML, DDL and DQL are ultimately all SQL. These are considered sublanguages of SQL. In fact, many people who write SQL day-to-day might not be aware of these terms and simply refer to all of them collectively as SQL.

DQL stands for Data Query Language and this is the most commonly used part of SQL in practice. With DQL you can:

  • get data to do some analysis or run a report using SELECT

DDL stands for Data Definition Language and this allows you to change objects in a database. With DDL you can:

  • create new objects like tables using CREATE
  • change existing objects, for example like adding a new column to a table, using ALTER
  • remove tables (be careful!) using DROP

DML stands for Data Modification Language and, as you’d expect, this is what you use to change existing data. With DML you can:

  • add new records to a table using INSERT
  • modify existing records in a table using UPDATE
  • remove a record from a table using DELETE

DQL is the most commonly used sublanguage of SQL in analytics roles, as it’s used right across the spectrum. DML and DDL, on the other hand, would not commonly be used by data analysts or data scientists, but instead by data engineers, SQL developers and other engineers who are responsible for storing the data.

What’s in the Alooba SQL test?

You can assess SQL in various ways on Alooba, including through the dedicated SQL coding environment and also the Concepts & Knowledge test type.

The Alooba SQL test is fully customizable, giving you the freedom to set the difficulty level, number of questions, timing & topics covered. You can assess anything from basic selects, to complex correlated subqueries and windowed aggregates. You can also assess DML actions like updating, inserting and deleting records.

Here’s a quick walkthrough video of the Alooba SQL test. In it, you’ll get a glimpse into the Alooba SQL test environment, the types of questions, learn how to test your code, how to explore the data, the state of the data and how the tables will be shown. You’ll also see the feedback hints shown to candidates when they’re submitting queries.

Here’s a free practice SQL test. Candidates can take this to gain practice before taking a real test. Hiring managers can check out this free practice test to get a glimpse into how the test works.

What’s the main features of the Alooba SQL test?

With the Alooba SQL test, it comes with full customization ability (questions, timing, length, difficulty etc.), advanced cheating prevention, automated grading, a comprehensive bank of different questions, and a simple integrated development environment.

You can see all the features of Alooba products here.

Here’s a quick walkthrough video of the Alooba SQL test.

Is this an online SQL test?

Yes, the Alooba test is delivered fully online, perfect for remote hiring and employees working from home. Testing online gives you the ability to scale your hiring process exponentially. No more bringing candidates into an office one-by-one.

How do you prevent cheating on the SQL test?

Alooba has various types of advanced cheating prevention. In order to retain the integrity of our methods, we do not disclose these publicly. Speak to your Alooba account manager to learn more.

What types of SQL questions do you have?

Alooba comes with an extensive array of SQL questions to assess your candidates and employees.

Each SQL question relates to a small database of 3-4 different tables, presented in an ERD (Entity Relationship Diagram), which is basically just a special type of picture that shows how the tables relate to each other.

The questions range in difficulty. An ‘easy’ question might be where candidates need to, for example, find which store had the highest number of sales in a particular month. So this is a simple select with a filter.

A ‘hard’ question might require the candidates to do various complex joins and a windowed aggregate to find the running total of sales per day, for example.

You can also choose DML questions, which require candidates to modify data through updates, inserts and deletes.

In addition to the questions in Alooba, you also add your own organization-specific SQL questions to extend the library. Some organizations choose to do this so that their candidates and employees can take tests with real data that they would use - or do use - day-to-day.

What type of SQL does this assess?

The Alooba SQL test runs on SQL-lite, which is an open source version of SQL. There are some syntactical differences between all versions of SQL, but they are 95% the same. This test is appropriate if your SQL version is: T-SQL (Microsoft SQL Server), Redshift, MySQL, PostgreSQL, Snowflake, Oracle, Google Big Query and many others.

Where can I access the Alooba SQL test?

Looking to assess your candidates? Reach out to us here to get started.

Can I see a preview of the Alooba SQL test?

You sure can, check out this quick video walkthrough, or take this free SQL practice test.

Do you have a SQL Server test?

There are various different versions of SQL, all of which are based on ANSI SQL. SQL Server is a particular type of Relational Database Management System, and it has a proprietary version of SQL called T-SQL (Transact-SQL).

The best analogy for this is spoken languages like English. You can speak Australian-English, American-English, Candidate-English, Scottish-English etc. While there are subtle differences between each of these, ultimately it’s all the same language. Same goes for SQL.

The Alooba SQL test runs on SQLite, which is very similar to any other version of SQL. The Alooba SQL test is therefore appropriate to assess your candidates’ SQL Server skills.

Do you have an Oracle SQL test?

There are various different versions of SQL, all of which are based on ANSI SQL. Oracle SQL Developer is a particular type of Relational Database Management System, and it has a proprietary version of SQL called Oracle SQL.

The best analogy for this is spoken languages like English. You can speak Scottish-English, New Zealand-English, South African-English, Welsh-English etc. While there are subtle differences between each of these, ultimately it’s all the same language. This is the same for SQL.

The Alooba SQL test runs on SQLite, which is very similar to any other version of SQL. The Alooba SQL test is therefore appropriate to assess your candidates’ Oracle SQL skills.

What level of difficulty is the SQL test?

The SQL test can be customized to suit any level of difficulty, from beginner to advanced.

Each question on Alooba has a difficulty rating of ‘easy’, ‘medium’ or ‘hard’. You can customize your assessment to include whichever questions you like. Most assessments our customers choose to create will include a blend of questions of various levels of difficulty.

We have pre-built templates to get started testing in 2-clicks. These range from beginner SQL, intermediate SQL to advanced SQL.

How long does the SQL test last?

You can customize your Alooba SQL test to make it as long or as short as you want. Really, the length you set depends on how you want to use the SQL test.

If you’re looking to assess candidates and replace manual CV screening, we’d suggest a short, sharp SQL quiz.

If you’re using the SQL test to replace a take-home SQL test, then we’d suggest making it more in-depth, potentially combining the SQL test with a Concepts & Knowledge test.

What roles is this test suitable for?

SQL is a must-have for pretty much all analytics roles. This includes: data analyst, data scientist, data engineer, product analyst, business intelligence analyst and growth analyst. The types of things that a data engineer needs SQL for is quite different to a data analyst. The Alooba questions cover a broad range of different SQL tasks that are relevant to the different roles.

How much does the SQL test cost?

There are various commercial options available, and we work with organizations of all types, from startup, to scale up, to government, to non-profit and of course large enterprise. We’d encourage you to book a quick 15-minute discovery call to learn more.

What should I look out for on a candidate’s CV?

In general, we’d recommend avoiding screening candidates based on their CV. Here’s an extensive discussion of the issues around manual CV screening, including why it’s both biased and inaccurate.

How do data analysts, data engineers and data scientists use SQL?

SQL is generally considered an essential skill for a data analyst. A truly non-negotiable skill.

The types of tasks that a data analyst uses SQL for does vary a lot compared to data engineers, data scientists, SQL developers and BI developers, in particular.

A data analyst will mainly be using SQL to query the database to:

  • build & modify datasets for dashboards and reports
  • run ad hoc queries to do some analysis

As a result, data analysts would mainly focus on selecting data, rather than creating objects or modifying data. That is, they will do more DQL than DDL or DML.

A data scientist will tend to be focused on DQL as well. Data scientists would normally then do their advanced analysis and build their machine learning models in Python or R. SQL is rarely used for statistical analysis or machine learning.

A data engineer, on the other hand, is often responsible for maintaining datasets, data models and data pipelines. They will then need to do more DDL (creating and maintaining objects in a database) and DML (updating existing data).

How should I assess someone’s SQL skills?

Understanding someone’s SQL skills is best done through a practical test, rather than an interview.

Whatever SQL test option you choose, you should make sure that the SQL test:

  • gives you the ability to assess candidates at scale with automated grading.
  • gives you the ability to assess candidates objectively and impartially through automated grading.
  • includes relevant questions that assess typical things you’d do day to day as a data analyst, data scientist or data engineer.
  • gives you the insights needed to make an informed hiring decision.

Check out the free Alooba SQL test to get a glimpse into how it works.

Check out the quick explanatory video to get a walkthrough of the SQL testing environment.

Can I test relational database skills?

Yes absolutely, this is also a skill you can assess on Alooba. Testing SQL in combination with Relational Databases is quite common for Alooba customers. They go hand-in-hand because SQL is the language you use to interact with relational databases.

The Relational Databases skill is tested within the Concepts & Knowledge quiz.

Can I test other skills as well?

Yes, you can test more than 40+ skills on Alooba, one of which is SQL. Most customers choose to assess their candidates & employees in the 4-8 most critical skills for that role. This gives them a much broader understanding of their strengths and weaknesses, which helps make better hiring and training decisions.

Can I add my own SQL questions?

Yes, you can. With Alooba’s Question Bank, you can add your own SQL questions. You might like to include data from your organization, so that candidates can get a glimpse into the types of data and problems that they will solve on the job in your organization. If you’re testing your employees using Alooba Growth, this also gives them a chance to use the datasets that they’re already familiar with.

Why can’t I just ask my candidate SQL questions in the interview instead?

Interviews are generally not considered the best way to assess someone’s SQL skills, or any coding skills for that matter. Talking through something, using a whiteboard, using pen and paper or having someone breath down your neck as you’re trying to write SQL are unsavory experiences for many candidates, especially introverts or those with social anxiety.

We’d generally recommend assessing SQL skills in a test environment, which better matches how someone would write SQL on the job.

If you are going to assess someone’s SQL skills in an interview anyway, we’d recommend doing at least the following:

  • ensuring the candidates are all asked the same questions as each other
  • using a pre-defined common scoring rubric for each question

These are some basic elements of structured interviews, which are a great way to reduce bias and improve the accuracy of your hiring process. You can create and execute structured interviews using Alooba Interview.

Why can’t I just give my candidates a paper and pen SQL test?

… :( :( :( Come on, seriously. It’s 2022, and you’re still doing pen and paper tests? Why? Ask yourself that question first please :)

If you are still not convinced, feel free to reach out to us to book a discovery call and learn how to modernize your hiring process.

How is the Alooba SQL test graded?

The SQL test is automatically graded. Each SQL question on Alooba has an example query which correctly solves the problem. The output of the candidate’s query is compared against the output of the correct query. If the outputs match, the candidate is awarded full marks.

You can also award partial marks from the results page if you wish to.

Which companies use this SQL test?

The Alooba SQL test is used by the majority of our customers, including enterprises like Suncor Energy, Unilever, Bloomberg, Canva and Woolworths.

What about no-SQL?

No-SQL databases are different to relational databases. No-SQL databases are typically used to store unstructured data that doesn’t fit nicely into rows and columns.

On Alooba, you can assess MongoDB, for example, in our Concepts & Knowledge quiz. No-SQL concepts are also covered in the Data Management and Hadoop skills.

Can I assess my team with the Alooba SQL test?

Yes absolutely, you can assess your team’s SQL with Alooba Growth.

Is this a test for an SQL developer?

SQL Developer is one of the most commonly assessed roles on Alooba, and the SQL test is a great option. We’d recommend combining the SQL Test with a Concepts & Knowledge test covering other important skills for a SQL Developer like Data Modeling, Data Management, Relational Databases and Reporting & Visualizations.

Testing across multiple skills is essential to give you the best understanding of the candidate’s capabilities. We have pre-built SQL Developer role templates to get you started testing in 3 clicks.

Do you have SQL testing interview questions?

Yes, but we’d recommend assessing SQL within a test rather than an interview. Interviews are better for understanding experience, understanding a candidate’s motivations, building a relationship and assessing ‘soft’ skills like verbal communication.

You can run structured interviews with Alooba Interview.

How many candidates have taken the Alooba SQL test?

The Alooba SQL test has been battled-tested across more than 10 000 candidates and counting.

Alooba SQL Test Candidate FAQ

Is it worth learning SQL?

If you are hoping to have any data-related role, it is absolutely essential that you learn SQL. It’s also not actually that difficult, relatively speaking, to pick up.

Additionally, the return on investment is almost immediate. Unlike learning Python or R for example, even the absolute most basic SQL query is actually quite useful in practice. There’s not much benefit to printing ‘Hello World’ (the quintessential first lesson in programming), but selecting some data from a table, or making a small tweak to an existing query, is immediately useful.

How do I include SQL skills on my resume?

Once you complete your Alooba assessment, you’ll receive your results via email. You can include a link to your Alooba test results on your CV to validate your skills.

If you do describe your SQL skills, try to be more descriptive than ‘advanced’ or ‘intermediate’. The issue is that these descriptions are vague and mean different things to different people. This is why it’s important to quantify your skills.

How do I practice for the Alooba SQL test?

We’d recommend taking the free SQL practice test here.

You can also try the free data analysis test which includes some SQL MCQ questions too.

How do I test my SQL queries?

As you will see from the explanatory video, you can test your query by executing it as many times as you like. We only consider your final query when you submit the test or the test runs out.

Can I get a SQL test certificate or badge?

If you score well on an Alooba assessment, feel free to share this performance on your CV. Your results link is emailed to you after you complete your assessment. You can include this in your CV to signal to employers that you have already validated your SQL skills.

Do you have a free SQL test?

Yes we sure do, you can take the free Alooba practice SQL test as much as you like.

What are the common mistakes made in the Alooba SQL test?

The most common mistakes we see candidates make is to not show enough attention to detail when answering the question. Make sure you read the question very carefully. We recommend reading it out aloud so you can hear yourself describe the problem.

You can also execute your query as many times as you like, so we’d encourage you to do that to check the output.

How can I level up my SQL skills?

Perfect practice makes perfect, as they say. Put down the books and pause the YouTube videos, and start writing actual SQL. There’s some great practice databases out there on Kaggle and other places. Most relational management database systems also come with free versions, some with pre-loaded data, such as the Microsoft SQL Server’s AdventureWorks database.

Where are the SQL test answers?

In order to retain the integrity of our assessments, we do not release answers to our questions. This is part of our commitment to fairness and objectivity in hiring. Reach out to your Alooba account manager to learn more.

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