Mario,

Is there any reason why you are trying it this way?

You are updating a system table, which is generally not really
supported or the safest way of doing things.

> In Firebird 2, I am trying to increase the size of the existing field
> from 5 to 10 characters.
> The following SQL query does work, but only for a specific data set:
> update RDB$FIELDS set
> RDB$FIELD_LENGTH = 10,
> RDB$CHARACTER_LENGTH = 10,
> RDB$CHARACTER_SET_ID = NULL
> where RDB$FIELD_NAME = 'RDB$648'
>
> Other datasets that need to be updated automatically have different
> internal RDB$FIELD_NAME numbers (i.e. different from RDB$648)
> The actual name of the field is LITTERMARK and the table name is
> PROGENY. The field type is VARCHAR (5).
> I have tried the following, but it does not work:
> update RDB$FIELDS set RDB$FIELD_LENGTH = 10, RDB$CHARACTER_LENGTH = 10
> where (RDB$FIELD_NAME = 'LITTERMARK') and (RDB$RELATION_NAME = 'PROGENY')

Could be because the field_name isn't the same as in the table :)

> How to structure this query to change the LITTERMARK field size in a
> generic way, irrespective of the internal RDB$FIELD_NAME number ?

Martijn Tonies
Database Workbench - development tool for Firebird and more!
Upscene Productions
http://www.upscene.com
My thoughts:
http://blog.upscene.com/martijn/
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