Data Quality Analyst Interview Questions and Answers for Freshers

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

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

Window functions in SQL are used to perform calculations across a set of table rows related to the current row.

• Window functions are used to calculate values based on a specific subset of rows within a result set.

• They do not cause rows to become grouped into a single output row like aggregate functions.

• Common window functions include ROW_NUMBER(), RANK(), DENSE_RANK(), and NTILE().