[Solved] Find the error in this query:SELECT dept.name, emp_count FROM (SELECT department_id, COUNT(*) AS emp_count FROM employees GROUP BY department_id) dept_emp JOIN departments ON dept_emp.... | SQL

SQL - Subqueries

Find the error in this query:

SELECT dept.name, emp_count FROM (SELECT department_id, COUNT(*) AS emp_count FROM employees GROUP BY department_id) dept_emp JOIN departments ON dept_emp.department_id = departments.id;

AGROUP BY clause is missing

BIncorrect alias for subquery

CMissing alias for departments table

DJOIN condition is invalid

Step-by-Step Solution

Solution:

Step 1: Check table aliases in query
The subquery is aliased as dept_emp, but the departments table is used without alias.
Step 2: Identify usage of alias in SELECT
The SELECT clause uses 'dept.name' but 'dept' alias is not defined for departments table.
Final Answer:
Missing alias for departments table -> Option C
Quick Check:
Alias used in SELECT must be defined in FROM/JOIN [OK]

Quick Trick: Alias all tables used in SELECT clause [OK]

Common Mistakes:

MISTAKES

Using undefined alias in SELECT
Assuming alias is optional when referenced
Confusing alias names between tables

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Find the error in this query:

Step 1: Check table aliases in query

Step 2: Identify usage of alias in SELECT

Final Answer:

Quick Check:

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