InsertQuery   (children 3)
 Identifier test_null_as_default
 ExpressionList (children 1)
  Identifier a
 SelectWithUnionQuery (children 1)
  ExpressionList (children 2)
   SelectQuery (children 1)
    ExpressionList (children 1)
     Literal \'HELLO\'
   SelectQuery (children 1)
    ExpressionList (children 1)
     Literal NULL
