ANDNR SOFT SOLUTIONS ETL Tester Interview Questions and Answers

Referential integrity ensures that relationships between tables are maintained in a database.

• It ensures that foreign key values in one table match primary key values in another table.

• It helps maintain consistency and accuracy of data in the database.

• If a foreign key value is deleted or updated, the corresponding primary key value should also be updated or deleted to maintain integrity.

Types of schema include star schema, snowflake schema, and fact constellation schema.

• Star schema: central fact table connected to dimension tables in a star-like structure.

• Snowflake schema: normalized form of star schema with dimension tables further normalized.

• Fact constellation schema: multiple fact tables share dimension tables.

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.

Snowflake schema is a normalized form of star schema with additional dimension tables.

• Snowflake schema is a data modeling technique used in data warehousing.

• In snowflake schema, dimensions are normalized into multiple related tables.

• Snowflake schema reduces redundancy and improves data integrity.

• Star schema is a denormalized form of snowflake schema with a single dimension table.

• In star schema, dimensions are not norma...read more

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