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Which SQL syntax correctly shows a correlated subquery?

easy📝 Syntax Q3 of 15
SQL - Subqueries
Which SQL syntax correctly shows a correlated subquery?
ASELECT e.name FROM employees e WHERE e.salary > (SELECT AVG(salary) FROM employees)
BSELECT e.name FROM employees e WHERE e.salary > (SELECT AVG(salary) FROM employees WHERE department = e.department)
CSELECT name FROM employees WHERE salary > 50000
DSELECT name FROM employees WHERE salary IN (SELECT salary FROM employees)
Step-by-Step Solution
Solution:

  1. Step 1: Identify correlation in subquery

    SELECT e.name FROM employees e WHERE e.salary > (SELECT AVG(salary) FROM employees WHERE department = e.department)'s subquery references e.department from the outer query, making it correlated.

  2. Step 2: Check other options

    The remaining options do not reference outer query columns inside the subquery.

  3. Final Answer:

    SELECT e.name FROM employees e WHERE e.salary > (SELECT AVG(salary) FROM employees WHERE department = e.department) -> Option B

  4. Quick Check:

    Correlated subquery syntax = references outer alias [OK]
Quick Trick: Look for outer query alias inside subquery WHERE clause [OK]
Common Mistakes:
MISTAKES
  • Missing outer query alias in subquery
  • Confusing simple subquery with correlated
  • Incorrect alias usage

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