Defensive Database Programming - Red Gate Software

Chapter 1: Basic Defensive Database Programming TechniquesThis time, only the description of Indiana is updated. In a similar fashion, we couldfilter out (i.e. ignore) ambiguities with the help of an analytical function, as shown inListing 1-28.-- rerun the code from Listing 1-22-- before executing this codeBEGIN TRAN ;WITH c AS ( SELECT c.Code ,c.Description ,s.Description AS NewDescription ,COUNT(*) OVER ( PARTITION BY s.Code )AS NumVersionsFROM dbo.Codes AS cINNER JOIN dbo.CodesStaging AS sON c.Code = s.Code)UPDATE cSET Description = NewDescriptionWHERE NumVersions = 1 ;ROLLBACK ;Listing 1-28: Using PARTITION BY to ignore ambiguities when updatingan inline view.In some cases, the approach of only performing unambiguous updates, and silentlyignoring ambiguous ones, is unacceptable. In the absence of built-in methods, we canuse tricky workarounds to reuse the code as much as possible and still raise an error ifthere is an ambiguity. Consider the example shown in Listing 1-29, in which a divide byzero occurs if there is an ambiguity.-- rerun the code from Listing 1-22-- before executing this codeDECLARE @ambiguityDetector INT ;WITH c AS ( SELECT c.Code ,c.Description ,52