Norstella ETL Tester Interview Questions and Answers

Project architecture refers to the overall structure of a software project, including components, modules, and their interactions.

• Project architecture defines how different components of a software project are organized and interact with each other.

• It includes the high-level design of the system, such as the database structure, data flow, and integration points.

• Project architecture also involves decisions on technologi...read more

Challenges in ETL testing include data quality issues, complex transformations, and handling large volumes of data.

• Data quality issues such as missing or incorrect data can impact testing results

• Complex transformations can be difficult to validate and may lead to errors in the ETL process

• Handling large volumes of data can slow down testing processes and require efficient testing strategies

Roles and responsibilities refer to the tasks and duties assigned to an individual within a specific job or position.

• Roles define the position or job title of an individual within an organization.

• Responsibilities outline the specific tasks, duties, and expectations associated with that role.

• Roles and responsibilities help clarify expectations, define boundaries, and ensure accountability.

• Examples include testing data e...read more

Use a dictionary to find duplicate values in an array of strings in Python.

• Create an empty dictionary to store the count of each string in the array.

• Iterate through the array and for each string, check if it exists in the dictionary. If it does, increment the count. If not, add it to the dictionary with a count of 1.

• After iterating through the array, check the dictionary for any strings with a count greater than 1. The

A deferred bug is a bug that is not fixed immediately but is scheduled to be fixed in a future release.

• Deferred bugs are usually lower priority bugs that do not impact the core functionality of the system.

• These bugs are documented and tracked for resolution in a later release.

• Examples of deferred bugs include cosmetic issues, minor usability problems, or non-critical functionality issues.

Use SQL query with ORDER BY and LIMIT to get 4th highest row based on a column

• Use ORDER BY clause to sort the column in descending order

• Use LIMIT 1 OFFSET 3 to get the 4th highest row

• Example: SELECT * FROM table_name ORDER BY column_name DESC LIMIT 1 OFFSET 3

SCD Type 2 stands for Slowly Changing Dimension Type 2, which is a data warehousing concept used to track historical changes in data.

• SCD Type 2 maintains historical data by creating new records for changes and preserving old records

• It includes additional columns like start date, end date, and version number to track changes

• Example: If a customer changes their address, a new record is created with the updated address wh...read more

Query to find duplicates in a database table

• Use GROUP BY and HAVING clause to identify duplicate records

• Select columns to check for duplicates

• Use COUNT() function to count occurrences of each unique value

Use SQL query with ORDER BY and LIMIT to fetch nth highest salary

• Use ORDER BY salary DESC to sort salaries in descending order

• Use LIMIT n-1,1 to fetch the nth highest salary

• Replace n with the desired position of the salary

Use SQL query to fetch the number 3 from a database table.

• Use SELECT statement with WHERE clause to filter for the number 3

• Example: SELECT * FROM table_name WHERE column_name = 3

Inner join combines rows from two tables based on a related column between them.

• Inner join returns only the rows that have matching values in both tables

• It is used to retrieve data that exists in both tables

• Example: SELECT Orders.OrderID, Customers.CustomerName FROM Orders INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID;

Cross join combines each row from one table with each row from another table.

• Cross join produces a Cartesian product of the two tables involved.

• It does not require any common columns between the two tables.

• It can result in a large number of rows if the tables are big.

• Example: SELECT * FROM table1 CROSS JOIN table2;

Different types of data validation and checks in ETL testing include schema validation, data completeness checks, data transformation checks, and data quality checks.

• Schema validation ensures that the data conforms to the expected structure and format.

• Data completeness checks verify that all expected data is present and accounted for.

• Data transformation checks ensure that data is accurately transformed according to bus...read more

Slowly Changing Dimensions (SCD) include Type 1, Type 2, and Type 3 dimensions.

• Type 1: Overwrite existing data with new data, no history is kept.

• Type 2: Create a new record for each change, maintaining history.

• Type 3: Create a new attribute to store changes, keeping limited history.