AlterQuery  t_block_number_proj (children 2)
 ExpressionList (children 1)
  AlterCommand ADD_PROJECTION (children 1)
   Projection (children 1)
    ProjectionSelectQuery (children 2)
     ExpressionList (children 2)
      Identifier a
      Identifier b
     Identifier b
 Identifier t_block_number_proj
