Defensive Database Programming - Red Gate Software

Chapter 1: Basic Defensive Database Programming TechniquesSET ManagerID = @ManagerIDWHERE EmployeeID = @EmployeeID ;Listing 1-20: Using unambiguous search criteria.As long as EmployeeID is the primary key on the dbo.Employee table, this procedurewill work correctly.The problem of ambiguous updatesThe results of data modifications may be unpredictable in the hands of the carelessprogrammer. Let's consider a very common requirement: populating a permanent tablefrom a staging table. First of all, let's create our permanent table, Codes, and a stagingtable, CodesStaging, as shown in Listing 1-21. Note that CodesStaging does nothave a primary key. This is very common for staging tables, because data is often loadedinto such tables before detecting duplicates and other data integrity violations.CREATE TABLE dbo.Codes(Code VARCHAR(5) NOT NULL ,Description VARCHAR(40) NOT NULL ,CONSTRAINT PK_Codes PRIMARY KEY ( Code )) ;GOCREATE TABLE dbo.CodesStaging(Code VARCHAR(10) NOT NULL ,Description VARCHAR(40) NOT NULL) ;GOListing 1-21: Creating the Codes and CodesStaging tables.45