Difference in isnull syntax between SQL Server and Oracle case when else

Isnull () in sqlserver ()
Nvl () in Oracle ()
Nvl (expr1, expr2) If expr1 is null, the value of expr2 is returned; otherwise, the value of expr1 is returned.
Nvl2 (expr1, expr2, expr3) If expr1 is not null, the value of expr2 is returned; otherwise, the value of expr3 is returned.
Nullif (expr1, expr2) if the values of expr1 and expr2 are equal, null is returned; otherwise, the value of expr1 is returned.

Use Case when else in sqlserver:
Table name = case when a. colorder = 1 then D. Name else ''end,


Use Case when else in Oracle:
(Case when a. colorder = 1 then D. Name else ''end) as table name,