What Happens If NULL Values Are Involved In Expressions
Posted by Ganesh
25 Dec, 2011
If NULL values are used in expressions, the resulting values will be NULL values. In other words:► Arithmetic expressions with NULL values result NULL values.► Comparison expressions with NULL values result NULL values.► Logical expressions with NULL values result NULL values.The tutorial exercise shows you some interesting examples:SELECT NULL + NULL FROM DUAL; NULL SELECT NULL + 7 FROM DUAL; NULLSELECT NULL * 7 FROM DUAL; NULLSELECT NULL = NULL FROM DUAL; NULLSELECT 0 < NULL FROM DUAL; NULLSELECT '' > NULL FROM DUAL; NULLSELECT NULL AND TRUE FROM DUAL; NULLSELECT NULL OR TRUE FROM DUAL; 1 -- This is contradicting against the rules!
If NULL values are used in expressions, the resulting values will be NULL values. In other words:► Arithmetic expressions with NULL values result NULL values.► Comparison expressions with NULL values result NULL values.► Logical expressions with NULL values result NULL values.The tutorial exercise shows you some interesting examples:SELECT NULL + NULL FROM DUAL; NULL SELECT NULL + 7 FROM DUAL; NULLSELECT NULL * 7 FROM DUAL; NULLSELECT NULL = NULL FROM DUAL; NULLSELECT 0 < NULL FROM DUAL; NULLSELECT '' > NULL FROM DUAL; NULLSELECT NULL AND TRUE FROM DUAL; NULLSELECT NULL OR TRUE FROM DUAL; 1 -- This is contradicting against the rules!
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