[Solved] Identify the error in this query that uses a subquery:SELECT e.name FROM employees e WHERE e.department_id = (SELECT d.id FROM departments d WHERE d.... | SQL

SQL - Subqueries

Identify the error in this query that uses a subquery:

SELECT e.name FROM employees e WHERE e.department_id = (SELECT d.id FROM departments d WHERE d.name = 'Sales');
Assuming multiple departments can have the same name.

AThe subquery syntax is invalid.

BThe subquery returns multiple rows causing an error with '=' operator.

CThe main query is missing a JOIN clause.

DThe WHERE clause should use EXISTS instead of '='.

Step-by-Step Solution

Solution:

Step 1: Analyze subquery result
The subquery may return multiple department IDs if multiple departments are named 'Sales'.
Step 2: Understand '=' operator limitation
The '=' operator expects a single value, so multiple rows cause an error.
Final Answer:
The subquery returns multiple rows causing an error with '=' operator. -> Option B
Quick Check:
Multiple rows with '=' = error [OK]

Quick Trick: Use IN() for subqueries returning multiple rows [OK]

Common Mistakes:

MISTAKES

Using '=' when subquery returns multiple rows
Assuming subquery always returns one row
Ignoring error messages about subquery results

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More SQL Quizzes

Identify the error in this query that uses a subquery:

Step 1: Analyze subquery result

Step 2: Understand '=' operator limitation

Final Answer:

Quick Check:

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