Firebird SQL: Check if notNULL constraint is set for a specific column?

Question

I want my C# program to know if the notNULL constraint is set for a specific Firebird database column. Can it be checked dynamically, perhaps by querying the meta data? I find the Firebird documentation to be very sparse.

Also, how does Firebird provide information what columns exist in a specific table?

Answer 1

Ok, didn't find it by using Stackoverflow's internal search, but by changing keywords in Google: How to check if NOT NULL constraint exists

Answer 2

Here is a Firebird Null Guide

http://www.firebirdsql.org/manual/nullguide.html

Answer 3

You need to request Firebird metadata about constraints — all information about it is stored in system tables. For example how to do that look at this page: http://www.alberton.info/firebird_sql_meta_info.html (see "List CONSTRAINTs" section).

Answer 4

To do it manually, use the following statement:

select rdb$null_flag
from rdb$relation_fields
where rdb$relation_name = 'MyTable' and rdb$field_name = 'MyField'

Alternatively you may try exploring FbDataReader.GetSchemaTable().