Data Quality Analyst Interview Questions and Answers

Different types of joins in SQL include inner join, outer join, left join, and right join. Handling duplicates can be done using DISTINCT keyword or GROUP BY clause.

• Types of joins in SQL: inner join, outer join, left join, right join

• Handling duplicates in SQL: use DISTINCT keyword or GROUP BY clause

• Handling duplicates in Excel: use Remove Duplicates feature

To find the product wise second highest sales item, sort the sales data for each product and select the second highest value.

• Sort the sales data for each product in descending order

• Select the second value from the sorted list to find the second highest sales item

• Consider ties and handle them accordingly

Pivoting a table in SQL involves rotating the data from rows into columns.

• Use the PIVOT keyword in SQL to pivot a table

• Specify the aggregation function and columns to pivot on

• Example: SELECT * FROM table_name PIVOT (SUM(value) FOR column_name IN (value1, value2, ...))

• Make sure to handle NULL values appropriately

Union combines and removes duplicates, Union All combines all rows including duplicates.

• Union combines the result sets of two or more SELECT statements and removes duplicates

• Union All combines the result sets of two or more SELECT statements including duplicates

• Union is slower than Union All as it involves removing duplicates