Question: When should I use the nvl
function as opposed to the nvl2 function. What is the
difference between nvl and nvl2?
Answer: The nvl
function only has two parameters while the nvl
parameter has three arguments. The nvl2 like like
combining an nvl with a decode because you can transform a value:
NVL ( expr1 , expr2 ):
If expr1 is null, then NVL returns expr2. If expr1 is not null,
then NVL returns expr1.
NVL2 ( expr1 , expr2 , expr3 ):
If expr1 is null, then NVL2 returns expr3. If expr1 is
not null, then NVL2 returns expr2
As we see, the vanilla
takes a NULL value and replaces it with a printable, useable value,
such as a zero or spaces:
select nvl(b.buffer_gets,0) – NVL replaces a NULL value with a
select nvl(current_status, “Not disclosed”) – NVL replaces a
NULL value with a string
Conversely, the NVL2 clause accepts three
arguments, but ALWAYS transforms the input argument.
select NVL2(supplier_city, 'Completed', 'n/a')
In this example, these statements are equivalent
because the nvl2 re-sets the input argument back to the original
select nvl(commission_pct,0) 2 from employees;
select nvl2(commission_pct,commission_pct,0) 2
these notes on advanced NULL operators in Oracle SQL.
Remember, that you can create an
on NULL values, using the nvl operator
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