Which SQL query correctly groups employees by their department_id and counts the number of employees in each department?

easy📝 Syntax Q3 of 15

SQL - GROUP BY and HAVING

Which SQL query correctly groups employees by their department_id and counts the number of employees in each department?

ASELECT department_id, COUNT(*) FROM employees GROUP BY department_id;

BSELECT department_id, COUNT(employee_id) FROM employees;

CSELECT department_id, COUNT(employee_id) FROM employees WHERE department_id GROUP BY employee_id;

DSELECT COUNT(employee_id) FROM employees GROUP BY department_id;

Step-by-Step Solution

Solution:

Step 1: Grouping by department_id
The query must group rows by department_id to count employees per department.
Step 2: Counting employees
Using COUNT(*) counts all rows in each group, which is appropriate here.
Final Answer:
SELECT department_id, COUNT(*) FROM employees GROUP BY department_id; -> Option A
Quick Check:
GROUP BY matches COUNT grouping [OK]

Quick Trick: COUNT(*) with GROUP BY groups rows correctly [OK]

Common Mistakes:

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