What Are NULL Values
Q
What Are NULL Values? - MySQL FAQs - Introduction to SQL Basics
✍: FYIcenter.com
A
NULL is a special value that represents no value. Here are basic rules about NULL values:
- NULL presents no value.
- NULL is not the same as an empty string ''.
- NULL is not the same as a zero value 0.
- NULL can be used as any data type.
- NULL should not be used in any comparison options.
- NULL has its own equality operator "IS".
- NULL has its own not-equality operator "IS NOT".
The tutorial exercise shows you some interesting examples:
SELECT 0 IS NULL FROM DUAL; 0 SELECT 0 IS NOT NULL FROM DUAL; 1 SELECT '' IS NULL FROM DUAL; 0 SELECT '' IS NOT NULL FROM DUAL; 1 SELECT NULL IS NULL FROM DUAL; 1 SELECT NULL IS NOT NULL FROM DUAL; 0
2007-05-11, 5311👍, 0💬
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