Which SQL query correctly calculates the percentage contribution of each product's sales to the total sales using window functions?

easy📝 Syntax Q3 of 15

SQL - Advanced Window Functions

ASELECT product, sales, (sales * 100.0) / SUM(sales) OVER () AS pct_total FROM sales;

BSELECT product, sales, (sales / SUM(sales)) * 100 AS pct_total FROM sales GROUP BY product;

CSELECT product, sales, SUM(sales) OVER (PARTITION BY product) / 100 AS pct_total FROM sales;

DSELECT product, sales, sales / SUM(sales) FROM sales;

Step-by-Step Solution

Solution:

Step 1: Identify correct window function usage
SELECT product, sales, (sales * 100.0) / SUM(sales) OVER () AS pct_total FROM sales; uses SUM(sales) OVER () to get total sales across all rows.
Step 2: Calculate percent of total
Multiplying by 100.0 converts fraction to percentage.
Step 3: Check other options
SELECT product, sales, (sales / SUM(sales)) * 100 AS pct_total FROM sales GROUP BY product; incorrectly uses GROUP BY without window function; SELECT product, sales, SUM(sales) OVER (PARTITION BY product) / 100 AS pct_total FROM sales; misuses PARTITION BY; SELECT product, sales, sales / SUM(sales) FROM sales; lacks window function.
Final Answer:
Option A -> Option A
Quick Check:
Window sum over all rows with multiplication by 100 [OK]

Quick Trick: Use SUM() OVER () for total sum [OK]

Common Mistakes:

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