LLD - Design — Food Delivery System
If a review system stores reviews in a SQL table with columns (user_id, product_id, rating, review_text), which SQL query retrieves the average rating for product_id = 101?
If a review system stores reviews in a SQL table with columns (user_id, product_id, rating, review_text), which SQL query retrieves the average rating for product_id = 101?
medium📝 Analysis Q5 of Q15
Step-by-Step Solution
Solution:
Step 1: Identify the goal
We want the average rating for product 101.Step 2: Choose SQL aggregate function
AVG(rating) calculates average rating; filter by product_id = 101.Final Answer:
SELECT AVG(rating) FROM reviews WHERE product_id = 101; -> Option BQuick Check:
Average rating query = SELECT AVG(rating) [OK]
Quick Trick: Use AVG() with WHERE for product filtering [OK]
Common Mistakes:
MISTAKES- Using COUNT instead of AVG
- Filtering by user_id instead of product_id
- Selecting all reviews without aggregation
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