Question

Bit rusty in sql

I have a situation where I need to insert a field “@Amount” into a temp table.If @amount from tableA is null or 0 get it from tableB

This is a simplified example of what I am doing.This must be done within a select statement when inserting into #CustomerTable
Do I need a case when statement?

DECLARE @Amount DECIMAL(18,4) 

SELECT @Amount=Amount
FROM TableA

INSERT #CustomerTable(id,Name,Amount)
SELECT 1,CustomerName,--if Amount is null or 0 get it from TableB else Get it from Table A.
FROM TableB

Answer 1

Since you’re using 2008 I’d twist the new NULLIF() function with the ISNULL() function and use a subquery:

insert @CustomTable (id, name, amount)
select
    1,
    CustomerName,
    ISNULL(NULLIF(TableA.Amount,0),(select Amount from TableB where TableB.ID = TableA.ID))
from
    TableA