SQL Server : IF null Replace with other column data

Question

I'm really new to SQL Server. I want to replace a null column with another column's data in the same table.

Declare @ref As mgr.gl_jlhdr.ref_no
Declare @P_no As mgr.gl_jlhdr.jlno

IF ref = Null
Then ref = P_no
end if

Please help.

I get an error

The type name 'mgr.gl_jlhdr.ref_no' contains more than the maximum number of prefixes. The maximum is 1.

What I want is to replace a null value column with other column data.

Example

if reference_no is null, I want it to use Product_no data.

Answer 1

In a query, you would do this with coalesce():

select coalesce(reference_no, product_no)
from mgr.gl_jlhdr;