>>Use 5 as a rule. Everything greater than 5 should be varchar.
>
>Are there any special consideration when updating the type of an actual field into varchar?

The safer method will be to create a new varchar field, update it with rtrim of old character field, then drop the original fied and rename the new field. This is assuming we don't have an index on that field.

It is always a good idea to use the good design from the beginning that changing the structure after the tables are populated.

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Anyway, you may try changing one of the tables in SSMS, saving the script, then verifying the length of the data in the columns.