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Easy#database

NULL trong SQL là gì và tại sao không thể dùng toán tử `=` để so sánh với NULL?

February 15, 2026

Quick summary

In SQL, NULL represents an "unknown" or "missing" value. Due to SQL's Three-Valued Logic (3VL), you must use the `IS NULL` or `IS NOT NULL` operators instead of the `=` operator to check for NULL.

Sample answer:

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam.

Quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore.

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