[Solved] Consider two tables: employees (5000 rows) and departments (50 rows). Which join order will likely reduce query execution time?Query A: SELECT * FROM employees JOIN departments ON employees.... | SQL

SQL - Advanced Joins

Consider two tables: employees (5000 rows) and departments (50 rows). Which join order will likely reduce query execution time?

Query A: SELECT * FROM employees JOIN departments ON employees.dept_id = departments.id;
Query B: SELECT * FROM departments JOIN employees ON employees.dept_id = departments.id;

AQuery B is faster because it starts with the smaller table

BBoth queries will fail due to join condition errors

CBoth queries run equally fast

DQuery A is faster because it starts with the larger table

Step-by-Step Solution

Solution:

Step 1: Understand join order effect
Starting with the smaller table allows filtering and reduces rows early in the join process.
Step 2: Compare queries
Query A starts with employees (5000 rows), Query B starts with departments (50 rows). Query B is more efficient.
Final Answer:
Query B is faster because it starts with the smaller table -> Option A
Quick Check:
Small table first improves speed [OK]

Quick Trick: Start joins with smaller tables for efficiency [OK]

Common Mistakes:

MISTAKES

Assuming larger table first is always better
Ignoring join condition correctness
Confusing query failure with performance

Master "Advanced Joins" in SQL

9 interactive learning modes - each teaches the same concept differently

Learn Why Deep Visual Try Challenge Project Recall Time

More SQL Quizzes

Consider two tables: employees (5000 rows) and departments (50 rows). Which join order will likely reduce query execution time?

Step 1: Understand join order effect

Step 2: Compare queries

Final Answer:

Quick Check:

Want More Practice?