[Solved] You have three tables: orders (10000 rows), customers (100 rows), and regions (10 rows). To optimize performance, which join order is best for:SELECT * FROM orders JOIN customers ON orders.... | SQL

SQL - Advanced Joins

You have three tables: orders (10000 rows), customers (100 rows), and regions (10 rows). To optimize performance, which join order is best for:
SELECT * FROM orders JOIN customers ON orders.cust_id = customers.id JOIN regions ON customers.region_id = regions.id;

AJoin regions to customers first, then join orders

BJoin customers to orders first, then regions

CJoin regions to orders first, then customers

DJoin orders to customers first, then join regions

Step-by-Step Solution

Solution:

Step 1: Analyze table sizes and join order
Orders is largest, customers medium, regions smallest. Joining orders to customers first reduces rows early.
Step 2: Join regions last
Joining regions last (smallest) after customers reduces join complexity and improves performance.
Final Answer:
Join orders to customers first, then join regions -> Option D
Quick Check:
Join large to medium first, then small [OK]

Quick Trick: Join largest tables first, smallest last for best speed [OK]

Common Mistakes:

MISTAKES

Joining smallest tables first causing repeated scans
Joining unrelated tables first
Ignoring table size in join order

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More SQL Quizzes

You have three tables: orders (10000 rows), customers (100 rows), and regions (10 rows). To optimize performance, which join order is best for:

Step 1: Analyze table sizes and join order

Step 2: Join regions last

Final Answer:

Quick Check:

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