What does the function NVL2 require regarding the datatypes of its parameters?

The function NVL2 requires that only value1 and value2 must match the datatype of the field. In NVL2, there are three parameters: value1, value2, and the alternative value that is returned when value1 is not null.

The fundamental purpose of the NVL2 function is to check whether a value (value1) is null. If value1 is not null, it returns value2; if value1 is null, it returns a third value, which can be any datatype. This allows for greater flexibility in the function's usage because it enables different datatypes in scenarios where they don't directly relate to the logical flow of the function based on the condition being evaluated.

Thus, the requirement that value1 and value2 should match the datatype of the field ensures that the function can operate correctly when returning results, aligning with the values being compared and the nature of any further operations that might incorporate these values. Importantly, this congruence prevents unexpected results caused by datatype mismatches in critical operations or comparisons.