Novice modding question

[Deadstarre]

Trying to remove a free promotion / building off the wonders, i'm getting database errors in the logging

[524098.671] Invalid Reference on Buildings.FreePromotion - "NULL" does not exist in UnitPromotions
[524098.671] Invalid Reference on Buildings.FreeBuildingThisCity - "NULL" does not exist in BuildingClasses

UPDATE Buildings
SET FreePromotion = 'NULL'
WHERE Type = 'BUILDING_STATUE_ZEUS';

UPDATE Buildings
SET FreeBuildingThisCity = 'NULL'
WHERE Type = 'BUILDING_GREAT_LIBRARY';

maybe relevant info from the game files

<Column name="FreeBuildingThisCity" type="text" reference="BuildingClasses(Type)" default="NULL"/>
<Column name="FreePromotion" type="text" reference="UnitPromotions(Type)" default="NULL"/>

    <Table name="UnitPromotions">
       <!-- Basic info -->
       <Column name="ID" type="integer" primarykey="true" autoincrement="true"/>
       <Column name="Type" type="text" notnull="true" unique="true"/>

I've tried 0, -1, false, NULL, leaving it blank, and they all work perfectly ingame to accomplish the task but give me the same errors. I really dont like errors, what am i missing here?

 

[LeeS]

NULL would be the correct designation in SQL, but 'NULL' is text whereas boolean NULL is not.

 

[Deadstarre]

NULL would be the correct designation in SQL, but 'NULL' is text whereas boolean NULL is not.

Smart. Thank you again