Initial values and Default Database values

Property inspector for an modelled attribute

DefaultDbValue

Initial value used when evolving the database or creating the database. If the attribute is nullable, i.e. has Allow Null = true, the DefaultDbValue is not needed

This value should be in the format expected by the database engine.

Examples using SQL Server;

• Non-nullable Boolean: 0 or 1

• Non-nullable Decimal: 0
• String: 'stringvalue' (quoted) (note: strings are always nullable if not using very old database types as char)

Initial value

Initial value used in-memory. Should be a value depending on type of attribute, or nothing/empty for null (if nullable).

Examples;

• Non-nullable Boolean: false or true

• Non-nullable Decimal: 0
• String: stringvalue (no quotes)

Allow Null

Controls both the in-memory nullability and database attribute setting.

If this is false, most database engines require a DefaultDbValue to evolve the database. If no value is provided, the existing rows (objects) in database will get an invalid value and the evolve will fail.