Top 10 SQL Interview Coding Questions for Data Analysts and Data Scientists

SQL Interview Coding Questions

SQL, or Structured Query Language, is the common language used for all databases. It is crucial in getting the necessary data out of the database. SQL is the high-level language that all big data technologies, including Hadoop and Spark, employ internally.

The only discipline that studies and analyses data is data science. To carry out a survey, the results of the data must be accurate and correct.

This is how SQL enters the data science picture. The principles are in SQL, even though some organizations have switched to NoSQL. Below are the top 10 interview questions for data scientists and analysts.

List of Common SQL Interview Questions

1. What are SQL’s most popular aggregation functions? How do they act?

An aggregate function adds together a group of values by performing a calculation on them and returning a single value. COUNT, SUM, and AVG are the three most popular aggregate functions in SQL. If you have gone through a Data Science Certification Program, you can answer it easily.

2. In SQL, What Is A Unique Key?

A record’s unique key in a database is made up of one or more columns or fields, According to SQL. Unique keys and main keys differ in that tables may include several unique keys. Only one NULL value may be used in a column with unique keys, and multiple NULL values are not permitted.

This is another common interview question asked by a data analyst or a data scientist.

3. What Makes A Table Different From A View?

Tables are composed of rows and columns and contain data. A view is a kind of virtual table that typically uses information from the table to display its contents.

If you wanted to look at a smaller subset of data from a table, that would be one use case for a view. The SELECT command could be used to query the data and generate a view.

4. To Update Data In A Table, What Command Would You Use?

With the SQL UPDATE command, you can modify an existing table. It is used to choose the specific instance along with SET (which contains the modified data) and WHERE.

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5. Why Does Denormalization Exist?

Denormalization is the name of the database optimization method when superfluous data is added to the table(s). The method is advantageous as it aids in lowering the expensive database joins.

6. What is Collation?

Collation gives the data in the database in a SQL Server Sorting Rules, accentuation, and case sensitivity features. Using collation to define the bit patterns, it represents each character in the database.

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7. What makes Union and Union All different from one another?

Union maintains unique records, as opposed to Union, which maintains all records, including all copies. Before returning the data, the union also performs a deduplication step, and the union always prints concatenated results.

8. How Can You Use SQL To Describe The Transpose Mechanism?

Changing a row or column into a certain format to see the data from a different angle is known as transposing in SQL. A simple transposition is from a row to a column or from a column to a row. Dynamic and linked transposition are common ways of transposition.

To analyze data and get a successful result, all transposition techniques are employed. Learn the concepts of data science by enrolling in a Data Science Course.

9. What Does the Price of a Database Index Mean?

It takes up a lot of room. The index will grow in size as your table does.

Our index must be updated whenever particular table rows are ADDED, DELETED, or UPDATED.

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10. What is ETL in SQL?

Extraction, Transformation, and Loading are known as ETL. For data analysis and visualization, it makes use of the data warehousing idea. It is used for data integration in a larger environment.

An ETL process is any system where data is transferred from one system to another destination system and saved there or copied, with the data being represented differently.

Conclusion

Knowing SQL is becoming more vital for data science and machine learning, in addition to Python or R proficiency. You can improve your performance at work and brush up on your SQL knowledge with the help of the above set of interview questions.

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