# SQL - Aggregations and Grouping (Data Analytics) > COUNT, SUM, AVG, MIN, MAX, GROUP BY, HAVING, nested aggregate functions, COALESCE, CASE WHEN - 20 interview questions - Junior - [Interview Questions: Data Analytics](https://sharpskill.dev/en/technologies/data-analytics/interview-questions.md) ## 1. Which SQL function counts the number of rows in a table? **Answer** COUNT is the SQL aggregate function that counts the number of rows returned by a query. COUNT(*) counts all rows including those with NULL values, while COUNT(column) only counts rows where the specified column is not NULL. ## 2. Which SQL function calculates the sum of values in a numeric column? **Answer** SUM is the aggregate function that adds up all non-NULL values in a numeric column. It is commonly used to calculate totals such as revenue, quantities sold, or any other cumulative value. If all values are NULL, SUM returns NULL. ## 3. What is the difference between COUNT(*) and COUNT(column)? **Answer** COUNT(*) counts all rows in the result, including those containing NULL values in any column. COUNT(column) only counts rows where the specified column has a non-NULL value. This distinction is essential when analyzing incomplete data. ## 17 more questions available - Which SQL function returns the average value of a numeric column? - What is the role of the GROUP BY clause in an SQL query? 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