T-sql case statement in a select

Question

When I execute the following t-sql 2012 statement, the "NO Prod' value is not
being displayed from the sql listed below:
SELECT DISTINCT
IsNull(cs.TYPE,'') as type,
CASE IsNull(Course.TYPE,'')
WHEN 'AP' then 'AP Prod'
WHEN 'IB' then 'IB Prod'
WHEN 'HR' then 'HR Prod'
WHEN '' then 'NO Prod'
END AS label
FROM CustSection cs
INNER JOIN dbo.Person p on P.personID = cs.personID
Left join customCustomer cs564 on cs564.personID = p.personID and
cs564.attributeID ='564'
   where ( cs.type is null and cs564.attributeID = null)    
     or
    (cs.type IN ('HR','AP') OR
      (cs.type='IB' AND SUBSTRING(cs.code,1,1)='3'))  
ORDER BY label
What I want is for 'NO Prod' to be displayed when
cs.type is null and cs564.attributeId  is null.
Thus can you tell me how to fix query above so the 'NO Prod'  value is displayed in the
select statement listed above?

Answer 1

There is no CASE statement in SQL; we have a CASE expression. We do not use the old 1970's Sybase*- ISNULL(); we have  COALESCE().
There is no such thing as a magic generic “type” in RDBMS. There is no such thing as a generic “code” in RDBMS. They have to to be “<something in particular>_type” and “<something in particular>_code” in a valid data model. How about blood_type
and postal_code?? 
There is no such thing as a generic “person” table in RDBMS. First of all, do you really have only one person, as you said?? But the important point is that these persons play a role in the data model – customers, students, etc. You are doing the wrong thing
and doing it badly.  This table should not exist any more than a  table of “Things” such exist. 
And the reason you are beyond any real help is “attribute_id” which tell us that your schema is a total disaster of data and meta data mixed together in a non-RDBMS written in awful SQL. Based on cleaning up bad SQL for 30 years, it looks like you are an OO
programmer who never unlearned his prior mindset. 
Why did you allow an encoding schema with blanks? Why do you have so many NULL-able columns? 
SELECT DISTINCT is very rare in a properly designed schema. The DRI references assure that rows cam be matched. To get you started, look at this skeleton:
CREATE TABLE Products
(product_gtin CHAR(15) NOT NULL PRIMARY KEY, 
 product_type CHAR(2) DEFAULT 'XX' NOT NULL
  CHECK (product_type IN ('AP', 'IB', 'HR', 'XX'))
The table name is a plural noun because it models a set (NOT an OO class).
The GTIN is an industry standard identifiers, and not have to invent our own.
The product_type (not blood_type, not automobile_body_type!) has a constraint that assures it is never NULL and never blank; I invented 'XX' as a default. 
You need more help than you can get in a forum, but if you will follow Netiquette and post the DDL, we can get you started.
--CELKO-- Books in Celko Series for Morgan-Kaufmann Publishing: Analytics and OLAP in SQL / Data and Databases: Concepts in Practice Data / Measurements and Standards in SQL SQL for Smarties / SQL Programming Style / SQL Puzzles and Answers / Thinking
in Sets / Trees and Hierarchies in SQL