| A | B |
|---|
| NVL | converts nulls to an actual value |
| COALESCE | returns the first non null expression in the list |
| NVL2 | examines the first expression; if the first expression is not null, it returns the second expression; if the first expression is null, it returns the third expression |
| NULLIF | compares two expressions; if they are equal, the function retyrns null; if they are not equal, the function returns the first expression |
| DECODE | compares an expression to each of the search values |
| Conditional expression | an if-then else expression whose value depends on the truth value of a Boolean expression |
| CASE | implements conditional processing within a SQL statement; it meets the ANSI standard |
| null | unknown |
