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copied!<p>Here are the guidelines I personally use regarding default values which have served me well in the past. In the following examples, consider a database backend with multiple applications with read/write access to the backend. In these cases it is essential that the database define how the data is to be modelled and therefore ensure data integrity. </p> <p>1) CreatedDate and ModifiedDate columns. These columns typically will have getdate() (sql server) defined as the default. As mentioned in other posts, these fields can then be updated with triggers etc.</p> <p>2) Boolean state columns. Examples: "IsDefault", "IsDeleted" (for auditing), "IsActive",etc. All of these fields will generally have a logical default state which should be defined by the data model. Exceptions to this would obviously be nullable tri-state boolean fields where the null state represents something about the data stored in the record.</p> <p>3) Data constraint definitions: Columns with AllowNull=false and no default defined. In other words, a value is required by the application. </p> <p>4) Lookup table foreign key identities: This is probably not the norm but for alot of lookup table foreign keys I will define a default that covers the initial state of a record. So for example, in an "Event" table the foreign key column "EventTypeId"(int-autoincrement) will have default 1 and represent "General" or something. This will cover most scenarios where, for instance, I want to log an event but dont care about a specific type id.</p> <p>5) Non-critical string columns: "Description", "Comment" etc. For these columns I will generally define '' as the default purely to simpify System.DbNull=>Null conversion handling in applications. This is something that may not be applicable in all scenarios especially when the table concerned contains millions of rows and storage space is an issue.</p> <p>So in summary, use defaults to ensure the data integrity of the actual data stored in the database. The data model should define these data integrity rules within itself and any application interacting with it will and should be forced to respect these rules. Also please note that this is not doctrine and that there will always be exceptions. Consider each scenario individually so that it makes sense for your database/application.</p>

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