Data Analyst and Team Lead Interview Questions and Answers

Types of joins in SQL include inner join, left join, right join, and full outer join.

• Inner join: Returns rows when there is a match in both tables.

• Left join: Returns all rows from the left table and the matched rows from the right table.

• Right join: Returns all rows from the right table and the matched rows from the left table.

• Full outer join: Returns rows when there is a match in either table.

• Example: Inner join - SELECT * FROM table1 INNER JOIN table2 ON table1.id = table2.i...read more

Use the DELETE statement with a self-join to remove duplicate rows in SQL.

• Use a self-join to identify duplicate rows based on a unique identifier column

• Use the DELETE statement with the self-join condition to remove the duplicates

• Example: DELETE FROM table_name WHERE id NOT IN (SELECT MIN(id) FROM table_name GROUP BY column1, column2)

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

• Window functions operate on a set of rows related to the current row

• They can be used to calculate running totals, moving averages, rank, etc.

• Examples include ROW_NUMBER(), RANK(), LAG(), LEAD()