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COAnswer is below, but first comment your answer.
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The correct answer is: B. No rows
SELECT *
FROM table_name
WHERE column_name = NULL
🔴 The key issue:
In SQL, NULL does not behave like a normal value.
* NULL means unknown / missing value
* You cannot compare NULL using = or !=
🧠 Why?
SQL follows three-valued logic:
* TRUE
* FALSE
* UNKNOWN
Any comparison with NULL results in UNKNOWN, like:
NULL = NULL → UNKNOWN
column_name = NULL → UNKNOWN
And in a WHERE clause:
* Only TRUE rows are returned
* FALSE + UNKNOWN are ignored
👉 So result = no rows
❌ Why other options are wrong:
* A. All NULL rows ❌
This would only happen with IS NULL, not = NULL
* C. Error ❌
Query is syntactically valid, so no error
* D. All rows ❌
Condition is never TRUE
💡 Interview Insight
This is one of the most commonly failed SQL questions.
Most people think:
“NULL = NULL should be TRUE”
But in SQL:
NULL is not equal to anything — not even itself
#sql #database #learncoding #codinginterview #learnsql
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@console.laugh
