SQL · Question 25 · Medium

SQL question 25

Table Orders:
order_id | customer | city | amount
101 | Meera | Chennai | 1200
102 | Arjun | Bengaluru | 600
103 | Meera | Chennai | NULL
104 | Sana | Delhi | 1100
105 | Arjun | Bengaluru | 600
106 | Dev | Bhopal | 300
107 | Sana | Delhi | 400

What does this query return?

SELECT COUNT(*)
FROM Orders
WHERE amount = NULL;
  1. 1
  2. 6
  3. 0
  4. 7
Answer and explanation

Answer: C. 0

Explanation: Any comparison with NULL using = gives UNKNOWN, never TRUE, so no row qualifies and the count is 0. To find the missing amount you must write amount IS NULL, which would return 1.

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