The following table defines the bindings between InterBase SQL datatypes and C# Object Type mappings using the InterBase Borland Data Provider (BDP). All C# client applications should consider using this table for data retrieval methods.

Option 1:
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Create a field of type CHAR and use CHECK CONSTRAINTS to limit
the values that are allowed to be entered into it.

Example:
	
      CHAR(1) CHECK (VALUE IN ("Y", "N")) NOT NULL;

Option 2:
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Similar to above but use a domain to create a global data type for
the database so that you may reuse the data type more easily.

Example:

      CREATE DOMAIN YN AS CHAR(1) CHECK(VALUE IN ("Y","N")) NOT NULL;