Hexaware Technologies ETL Tester Interview Questions, Process, and Tips

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

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

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