[Solved] Given the table sales with column amount containing values (100, 200, NULL, 300), what is the result of this query?SELECT COUNT(amount), SUM(amount), AVG(amount), MIN(amount), MAX(amount) FROM sales; | PostgreSQL

PostgreSQL - Aggregate Functions and GROUP BY

Given the table sales with column amount containing values (100, 200, NULL, 300), what is the result of this query?

SELECT COUNT(amount), SUM(amount), AVG(amount), MIN(amount), MAX(amount) FROM sales;

A(4, 600, 150, 100, 300)

B(4, 600, 200, 100, 300)

C(3, 600, 150, 100, 300)

D(3, 600, 200, 100, 300)

Step-by-Step Solution

Solution:

Step 1: Count non-null values in amount
Values are 100, 200, NULL, 300. COUNT(amount) counts non-null values = 3.
Step 2: Calculate SUM, AVG, MIN, MAX ignoring NULL
SUM = 100+200+300 = 600; AVG = 600/3 = 200; MIN = 100; MAX = 300.
Final Answer:
(3, 600, 200, 100, 300) -> Option D
Quick Check:
COUNT=3, SUM=600, AVG=200 [OK]

Quick Trick: Aggregate functions ignore NULL except COUNT(*) [OK]

Common Mistakes:

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Given the table sales with column amount containing values (100, 200, NULL, 300), what is the result of this query?