Defensive Database Programming - Red Gate Software

Chapter 1: Basic Defensive Database Programming TechniquesNow, let's populate each table with some sample data, as shown in Listing 1-22.DELETE FROM dbo.Codes ;INSERT INTO dbo.Codes( Code ,Description)SELECT 'AR' ,'Old description for Arkansas'UNION ALLSELECT 'IN' ,'Old description for Indiana' ;DELETE FROM dbo.CodesStaging ;INSERT INTO dbo.CodesStaging( Code ,Description)SELECT 'AR' ,'description for Argentina'UNION ALLSELECT 'AR' ,'new description for Arkansas'UNION ALLSELECT 'IN' ,'new description for Indiana ' ;Listing 1-22: Populating the Codes and CodesStaging tables.Now, we'll examine two different ways of updating data in the permanent table, basedon data in the staging table, both of which are subject to ambiguities if care is not taken.1. Using UPDATE…FROM.2. Updating an inline view.We'll then discuss strategies for avoiding such ambiguities.46