[Solved] Find the error in this query:SELECT * FROM employees WHERE department_id = (SELECT id FROM departments WHERE location = 'NY');Assuming multiple departments exist in NY. | PostgreSQL

PostgreSQL - Subqueries in PostgreSQL

Find the error in this query:

SELECT * FROM employees WHERE department_id = (SELECT id FROM departments WHERE location = 'NY');

Assuming multiple departments exist in NY.

ASubquery returns multiple rows causing error with '=' operator

BMissing WHERE clause in subquery

Cdepartment_id column does not exist

DNo error, query is correct

Step-by-Step Solution

Solution:

Step 1: Analyze subquery result
Subquery returns multiple department IDs for location 'NY'.
Step 2: Check operator compatibility
'=' expects a single value, but subquery returns multiple rows, causing error.
Final Answer:
Subquery returns multiple rows causing error with '=' operator -> Option A
Quick Check:
Use IN for multiple values, '=' for single value [OK]

Quick Trick: Use IN operator when subquery returns multiple rows [OK]

Common Mistakes:

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