Which of the following is the correct syntax to join two tables employees and departments on the column department_id?

easy📝 Syntax Q12 of 15

PostgreSQL - Joins in PostgreSQL

Which of the following is the correct syntax to join two tables employees and departments on the column department_id?

ASELECT * FROM employees JOIN departments ON employees.department_id = departments.department_id;

BSELECT * FROM employees WHERE department_id = departments.department_id;

CSELECT * FROM employees JOIN departments USING (department_id);

DSELECT * FROM employees JOIN departments ON employees.id = departments.id;

Step-by-Step Solution

Solution:

Step 1: Check the JOIN syntax with ON clause
The correct JOIN syntax uses ON to specify the matching columns: employees.department_id = departments.department_id.
Step 2: Verify other options
SELECT * FROM employees WHERE department_id = departments.department_id; uses WHERE incorrectly for joining. SELECT * FROM employees JOIN departments USING (department_id); uses correct USING syntax with parentheses. SELECT * FROM employees JOIN departments ON employees.id = departments.id; joins on wrong columns (id instead of department_id).
Final Answer:
SELECT * FROM employees JOIN departments ON employees.department_id = departments.department_id; -> Option A
Quick Check:
JOIN with ON correct columns = C [OK]

Quick Trick: Use ON with matching columns for JOINs [OK]

Common Mistakes:

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