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select NVL(NULL, 'A'),
NVL(TRIM(' '), 'A'),
COALESCE(NULL, 'A'),
COALESCE('', 'A')
from dual
| NVL(NULL,'A') | NVL(TRIM(''),'A') | COALESCE(NULL,'A') | COALESCE('','A') |
|---|---|---|---|
| A | A | A | A |