Hexaware Technologies ETL Tester Interview Questions and Answers

Common validation techniques in ETL testing include data completeness, data accuracy, data transformation, and data quality checks.

• Data completeness validation ensures that all expected data is loaded into the target system.

• Data accuracy validation involves verifying that the data is correctly transformed and loaded without any errors.

• Data transformation validation checks if the data is transformed according to the bus...read more

Use SQL query with ORDER BY and LIMIT to fetch 5th highest salary.

• Use ORDER BY clause to sort salaries in descending order

• Use LIMIT 1 OFFSET 4 to fetch the 5th highest salary

The SQL query to find records that never contain flag 0 in the critical column.

• Use the NOT EXISTS operator to check if there are no records with flag 0 for each distinct value in the critical column.

• Write a subquery to select distinct values from the critical column.

• Join the main table with the subquery using the critical column.

• Filter the result by checking if there are no records with flag 0 for each distinct value i...read more

To validate between two integers, compare each corresponding digit and check if they are equal.

• Convert both integers to strings

• Pad the source integer with leading zeros to match the length of the target integer

• Compare each digit of the source and target integers

• If any digit is not equal, the validation fails

Reorder a table to place 'India' at the top, followed by other countries.

• Use SQL to reorder the results: SELECT country FROM table ORDER BY CASE WHEN country = 'India' THEN 0 ELSE 1 END;

• This SQL query prioritizes 'India' by assigning it the lowest sort value.

• The rest of the countries will follow in their natural alphabetical order.

The question is asking to rearrange the numbers so that 100 is at the first row and the rest are below it.

• Create an array of strings to store the numbers

• Assign the value '100' to the first element of the array

• Use a loop to assign the numbers 1 to 99 to the remaining elements of the array

Set and join are operations used in database management systems.

• Set is used to perform mathematical set operations like union, intersection, and difference on two or more sets.

• Join is used to combine rows from two or more tables based on a related column between them.

• Set operations do not require a common column, while join operations do.

• Set operations return a result set with unique values, while join operations retur...read more

The output for inner join will be the rows where both col1 and col2 have non-null values.

• Inner join returns only the matching rows from both tables.

• In this case, the output will be the rows with non-null values in both col1 and col2.

• Rows with null or blank values in either col1 or col2 will be excluded from the output.

I worked on a data migration project for a retail company.

• Migrated data from legacy systems to a new ETL platform

• Ensured data integrity and accuracy during the migration process

• Created test cases and executed them to validate the data migration

• Collaborated with developers and business analysts to troubleshoot any issues

• Provided regular updates to stakeholders on the progress of the project

Scalar function is a function that returns a single value based on input parameters.

• Scalar functions are used in SQL to perform calculations on input values and return a single result.

• They can be used in SELECT statements, WHERE clauses, and other SQL queries.

• An example of a scalar function is the ABS() function, which returns the absolute value of a number.

Use regular expressions to extract numbers from alphanumeric data in a table.

• Use the REGEXP_REPLACE function in SQL to replace all non-numeric characters with an empty string.

• For example, SELECT REGEXP_REPLACE(column_name, '[^0-9]', '') FROM table_name;

• This will return only the numbers from the alphanumeric data in the specified column.

Query to fetch data greater than average, min and max salary.

• Calculate average, min, and max salary first

• Use a SELECT statement with WHERE clause to filter data greater than average, min, and max salary