What to put into lat/lng db fields if lat/lng are empty?

I have a mysql insert state开发者_如何学Goment that breaks when the system can't get lat/lng for a user. The sql loos like this:

INSERT INTO users(user_email, first_name , last_name , lat , lng ) values ( 'name'
 , 'email' ,  ,  );

What should I put into the lat/lng so that it doesn't break the insert statement like this? Should it be nulls? That seems kind of inappropriate to put nulls, no?

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Null is allowed if the table definition allows it. Null lat/long might mean that the user's location is unknown