Initial values and Default Database values
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==== DefaultDbValue ==== | ==== DefaultDbValue ==== | ||
Initial value used when evolving the database or creating the database. | 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 | This value should be in the format expected by the database engine. | ||
Examples using SQL Server; | |||
* Non-nullable [[Documentation:Boolean|Boolean]]: 0 or 1 | |||
* Non-nullable [[Documentation:Decimal|Decimal]]: 0 | |||
* String: 'stringvalue' (quoted) ('''note:''' strings are always nullable if not using very old database types as char) | |||
==== Initial value ==== | ==== Initial value ==== | ||
Initial value used in-memory. | Initial value used in-memory. Should be true/false or nothing for null (if nullable) or other value depending on type of attribute. | ||
Examples; | |||
* Non-nullable [[Documentation:Boolean|Boolean]]: false or true | |||
* Non-nullable [[Documentation:Decimal|Decimal]]: 0 | |||
* String: stringvalue (no quotes) | |||
==== Allow Null ==== | ==== Allow Null ==== | ||
Revision as of 16:47, 16 January 2024
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 true/false or nothing for null (if nullable) or other value depending on type of attribute.
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.
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