When you design the tables in your database, you determine which fields they contain. But you will often need to modify the design of some of the tables after they have been in use for a while. Typically you will want to add or delete fields, or make changes to field names or data types.
Rules for Changing Tables
You can modify tables that do not contain data at any time. However, when the table contains data, a number of restrictions apply. The following table lists some general rules.
Change a field name
You can always change the name of a field.
Change a field number
You can always change the number of a field. This causes Microsoft Dynamics NAV to run through all the application objects in order to update all the references to this field. This can be a time consuming process.
Change a field data type
You can change the data type for a field only if there is no data in this field for any of the records in the table. There is one exception to this rule—you can change the data type of a field from Code to Text even if the field contains data for some records.
Add a field to a table
You can always add a field to a table.
Delete a field
To delete a field, you must delete all data from the field in all records in the table. You must also remove all references to the field from other tables, pages, and reports.
Change the length of a String field
You can always increase the length of a String field. Whether you can decrease the length of a String field depends on the contents of all the values in the column in the table. The minimum length of a String field is determined by the longest string in the column.