I agree with PW,

Unless you made a typo you are not executing the same UDF that you posted

CREATE function ReFormatDate (@date varchar(15), @CurrentDate datetime)

Server: Msg 241, Level 16, State 1,...

Well based on what you have here you are stacking your if's and not nesting them.

Depending on what you desire.  It is hard to guess your logic without more info.

But...

DECLARE @salesDate DATETIME

DECLARE @salesPrice ???

SELECT @salesDate = sp1.salesDate, @salesPrice = sp1.salesPrice

FROM salesProduct sp1

WHERE sp1.salesDate = (

 SELECT MIN( sp2.salesDate )

 FROM salesProduct sp2

 WHERE sp2.saleProductId = sp1.saleProductId

)

AND sp1.salesProductId = 4

you said, "Think about the time saved for creating  screens for each reference table."

Well you must have spent time in building your own RI and you must have spent time...

My first reaction to this article was, Oh no not another Oracle DBA who was brought up on Forms.

The most common places I have seen this type of design is the "OLD"...