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Answer (Detailed Solution Below)

Option 2 : SELECT EName FROM Emp WHERE Comm <> 500 OR Comm IS NULL / SELECT EName FROM Emp WHERE Comm <> 500 OR Comm IS NULL

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Detailed Solution

सही उत्तर SELECT EName FROM Emp WHERE Comm <> 500 OR Comm IS NULL / SELECT EName FROM Emp WHERE Comm <> 500 OR Comm IS NULL है।

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Question:

In table Emp, some Comm values are NULL. Which query correctly lists employees whose commission is NOT 500, including those with unknown commission? / तालिका Emp में कुछ Comm मान NULL हैं। कौन-सी क्वेरी उन कर्मचारियों को सही सूचीबद्ध करती है जिनका कमीशन 500 नहीं है, अज्ञात कमीशन वाले सहित?

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SELECT EName FROM Emp WHERE Comm <> 500 / SELECT EName FROM Emp WHERE Comm <> 500
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SELECT EName FROM Emp WHERE Comm <> 500 OR Comm IS NULL / SELECT EName FROM Emp WHERE Comm <> 500 OR Comm IS NULL
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SELECT EName FROM Emp WHERE Comm != 500 AND Comm IS NULL / SELECT EName FROM Emp WHERE Comm != 500 AND Comm IS NULL
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SELECT EName FROM Emp WHERE NOT Comm = 500 AND Comm IS NOT NULL / SELECT EName FROM Emp WHERE NOT Comm = 500 AND Comm IS NOT NULL

Correct Answer: SELECT EName FROM Emp WHERE Comm <> 500 OR Comm IS NULL / SELECT EName FROM Emp WHERE Comm <> 500 OR Comm IS NULL

Comparisons with NULL yield UNKNOWN, so NULL rows are silently dropped by <>, and only an explicit OR Comm IS NULL brings them back; AND with IS NULL can never be true together with <>. / NULL से तुलना UNKNOWN देती है, इसलिए <> से NULL पंक्तियाँ चुपचाप छूटती हैं, और केवल स्पष्ट OR Comm IS NULL उन्हें लौटाता है; <> के साथ AND IS NULL कभी सत्य नहीं हो सकता।

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