SQL Server 2019

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

select coalesce(null, null)
Msg 4127 Level 16 State 1 Line 1
At least one of the arguments to COALESCE must be an expression that is not the NULL constant.

select coalesce(col1, col2)
from (values (null, null)) v(col1, col2)

(No column name)

null

declare @col1 int;
declare @col2 int;

select coalesce(@col1, @col2)

(No column name)

null