alter table imageT drop foreign key fk_imageT_nodeT1;
alter table imageT add constraint fk_imageT_nodeT1 
    foreign key (nodeId) 
    references nodeT (id) 
    on delete set null 
    on update no action;

/*    
SELECT * FROM imageT i
left join nodeT n on i.nodeId = n.id
WHERE n.id is null
*/