6 SQL Tricks Every Data Scientist Should Know

Data Scientist


It has been assumed that SQL is a required but uncool method of collecting data from databases to feed into fancier methods of data manipulation like pandas and tidyverse. SQL is, in certain respects, an underrated skill in data science. SQL is a database technology that is used in all job roles in software development.

Businesses require at least a basic understanding of SQL from data analysts, data scientists, and especially product managers. The standard query language is necessary for data processing, analysis, and slicing. Learning some hints about SQL, the data language, will help you create better dashboards and analyses in the future. Small changes in SQL can have a significant impact, whether they are made in the writing of data quality checks or even the avoidance of aggregating averages.

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SQL is the most effective data science foundation course to assist you in examining, filtering, and aggregating to acquire a complete knowledge of the data, even with the vast amounts of data being gathered or produced daily in the industries. By using SQL to slice and dice data, analysts can also find explorative patterns eventually, which frequently redefines the analysis population and variables to be relatively small.

Consequently, the first phase of analytics should be using SQL to extract insightful revelations from the data instead of moving enormous datasets to Python or R. Working with relational databases in the real world involves much more than just SELECT, JOIN, and ORDER BY operations.

In this article, you will go through six recommendations (plus one bonus tip) for using SQL for data science and combining it with other computer languages, such as Python and R, to improve the efficiency of your analytics work.

1. Missing Data/COALESCE() to recode NULL

The secret sauce is the COALESCE() function when recoding missing values. This function recodes NULL to the value specified in the second argument in such situations. In this example, NULL_VAR can be recoded to the character value “MISSING”.

2. Compute the cumulative frequency and running total

The cumulative frequency is calculated by adding every frequency out of a table of frequency distribution to the sum of its preceding. Due to the fact that all frequencies will now have previously been included in the prior total, the final result will constantly be equal to the average of all data.

3. Conditional WHERE clause

Choose a query with just a WHERE clause that demands a specific value, as in the name column that is supplied by a parameter. Therefore, in this instance, you would like the WHERE clause to be conditional, occasionally applying, and you also want to select all the database entries. Your first thought would be to just leave the parameter value blank. However, it would be clear if you put that to the test because returning no parameter value would result in no rows.

4. Lag() and Lead() operate on successive rows

Two of the most frequently utilised analytical functions in my day-to-day work were likely lag (looking at the previous row) and lead (looking at the next row). These two functions enable users to search several rows simultaneously without self-joining.

5. Integrate Python and R with SQL queries

The establishment of database connections using ODBC and JDBC is a need for integrating SQL queries within Python and R. The most straightforward approach to using a question in Python is to copy and paste it as a string and then call pandas. This assumes that we already linked Python and R to the database (); the approach works effectively as long as our queries are brief and finished without any alterations. What happens if our question has 1000 lines or needs to be updated frequently? In such cases, we might wish to read.sql files into Python or R directly.

6. Without self-joining, find the record(s) with the extreme values

For each unique ID, we are responsible for returning the row(s) with the highest NUM VAR value. A logical query would use ‘group by’ to determine the maximum value for each ID, followed by a ‘self join’ here on ID and the total value.

Advantages of Using SQL in Data Science

IBM created Structured Query Language, also known as SQL, in the 1970s as a query-oriented language for relational databases. It was developed using Relational Algebra, a cascading derivation from set theory and first-order logic. The popularity of SQL grew over time to the point where IBM was no longer the only company using it. It is used for data table pivoting and crossing by several well-used data analytics programmes, including R, SAS, and others.

The benefits of utilising SQL for data science may be summed up in two ways: how simple it is to use and how well it can help analysts understand the data sets. After all, every study, regardless of how complex, starts with the extraction and investigation of the data, which may involve structuring, cleaning, or crossing database tables. For instance, the R programming language includes a package called “sqldf” that enables the coding of SQL for the manipulation, crossover, and/or restructuring of Data Frames.


A Ph.D. or Master’s degree in statistics, computer science, or engineering is held by some data scientists. Any prospective data scientist can benefit from this educational background because it gives them a solid foundation and teaches them the fundamentals of Big Data and data scientist skills they need to be successful in their career. Some universities now provide specific programmes designed to meet the educational criteria for pursuing a career in data science. This has allowed students to concentrate on the subject they are most passionate about. If you want to make your career as a data scientist, start today by learning about the most fantastic SQL tricks. In addition to that, enrol in a data science foundation course by Great Learning that will encourage you to step forward towards career growth and success.




General FAQs

What data scientist should know in SQL?

A Data Scientist can control, define, manipulate, create, and query the database using SQL commands. Many modern industries have equipped their products data management with NoSQL technology but, SQL remains the ideal choice for many business intelligence tools and in-office operations.

Does a data scientist need to know SQL?

Machine learning and AI may dominate the tech headlines, but the most important skill in the data science industry is something much older – almost 50 years old, in fact! Despite its age, SQL is still the most important language for data work.

Do data scientists work with SQL?

Data scientists and data engineers, and indeed anyone with SQL skills – can work within the database, running ML models to answer almost any business question.


Devendra Singh

Director, Content Strategy at Digital Marketing Trends. I develop, evaluate, and improve the company's content strategies. Providing a big online presence for SMEs and StartUps.