Target Senior Data Scientist Interview Questions and Answers

Vlookup limitations include limited search range, case sensitivity, and inability to handle multiple matches.

• Vlookup only searches for values in the leftmost column of the table array

• It is case sensitive and cannot handle spelling errors

• It only returns the first match and cannot handle multiple matches

• It cannot search for values to the left of the lookup column

• It can be slow and inefficient for large datasets

Vlookup and Index-Match are both Excel functions used for lookup and retrieval of data.

• Vlookup is simpler and faster but has limitations in terms of flexibility and handling of large datasets.

• Index-Match is more versatile and can handle complex data structures but is slower and requires more effort to set up.

• Vlookup is best suited for simple lookups with small datasets while Index-Match is better for more complex looku...read more

Excel functions are pre-built formulas that perform calculations or manipulate data in a spreadsheet.

• Sum: adds up a range of numbers

• Sum if: adds up a range of numbers based on a specified condition

• Count: counts the number of cells in a range that contain numbers

• CountA: counts the number of cells in a range that are not empty

• Count Blanks: counts the number of empty cells in a range

SQL limitations include lack of scalability, security vulnerabilities, and difficulty in handling unstructured data.

• SQL is not suitable for handling unstructured data like images, videos, and audio files.

• It can be difficult to scale SQL databases to handle large amounts of data.

• SQL databases can be vulnerable to security threats like SQL injection attacks.

• SQL is not always the best choice for real-time data processing ...read more

Code to find duplicate records

• Identify the key columns to check for duplicates

• Use GROUP BY and HAVING clauses to filter out duplicates

• Consider using window functions like ROW_NUMBER() to identify and remove duplicates

• Use programming languages like SQL, Python, or R to write the code

Code to describe database and columns from a table

• Use SQL SELECT statement to retrieve column names and data types

• Use DESC command to get table structure

• Use INFORMATION_SCHEMA.COLUMNS to get detailed information about columns

• Use SHOW CREATE TABLE to get table creation statement

A trigger in SQL is a set of instructions that automatically executes in response to a specific event or action.

• Triggers can be used to enforce business rules, audit changes, or replicate data.

• They can be defined to execute before or after an INSERT, UPDATE, or DELETE statement.

• Triggers can also be nested, meaning one trigger can execute another trigger.

• Examples of triggers include sending an email notification when a ...read more

Stored procedures are precompiled SQL statements that can be reused and executed multiple times.

• Stored procedures improve performance by reducing network traffic and improving security.

• They can be used to encapsulate business logic and provide a consistent interface to the database.

• Stored procedures can also be used to simplify complex queries and transactions.

• Examples include procedures for inserting, updating, and de...read more

Data is collected from various sources including databases, APIs, and user input.

• We have access to multiple databases where we can extract relevant data

• We use APIs to gather data from external sources such as social media platforms

• Users can input data through forms or surveys

• We also collect data through web scraping techniques

As a data analyst, I face challenges such as data quality issues, incomplete or inconsistent data, and time constraints.

• Data quality issues: Dealing with missing or inaccurate data that can affect the analysis.

• Incomplete or inconsistent data: Working with datasets that are not complete or have inconsistencies, requiring data cleaning and manipulation.

• Time constraints: Balancing multiple projects and deadlines, often ne...read more

The sequence of execution of SQL codes is Select-From-Where-Group By-Having-Order By.

• Select: choose the columns to display

• From: specify the table(s) to retrieve data from

• Where: filter the data based on conditions

• Group By: group the data based on a column

• Having: filter the grouped data based on conditions

• Order By: sort the data based on a column

HAVING is used with GROUP BY to filter the results after grouping. WHERE is used to filter the results before grouping.

• HAVING is used with GROUP BY clause while WHERE is used with SELECT clause.

• HAVING is used to filter the results of aggregate functions while WHERE is used to filter individual rows.

• HAVING is used to filter the results after grouping while WHERE is used to filter the results before grouping.

• HAVING can o...read more

CSV files are plain text files that store tabular data, while Excel files are binary files that can contain multiple sheets and complex formatting.

• CSV files are simpler and more lightweight compared to Excel files.

• CSV files can be easily opened and edited using a text editor, while Excel files require specific software like Microsoft Excel.

• CSV files do not support formulas, macros, or formatting options like colors and...read more

I have handled large amounts of data in my previous roles.

• I have experience handling terabytes of data in my previous role as a data analyst at XYZ company.

• I have worked with data from various sources such as databases, spreadsheets, and APIs.

• I have also used tools like SQL, Python, and Excel to manipulate and analyze data.

• I am comfortable working with both structured and unstructured data.

• I have experience cleaning an...read more

Different approaches for data cleaning include removing duplicates, handling missing values, correcting inconsistent data, and standardizing formats.

• Remove duplicates

• Handle missing values

• Correct inconsistent data

• Standardize formats

• Use statistical methods to identify outliers

• Check for data accuracy and completeness

• Normalize data

• Transform data types

• Apply data validation rules