col-select-expr =

  ---> select-expr ------->

  select-expr =

  -+-+->  select-clause  ------------+-+------+
   | +-> ( select-expr )  -----------+ |      |
   | +->   TABLE table-ref ----------+ |      |
   +------ select-merge-clause <-------+      |
     +------------------- <-------------------+
     +-+--------------------+--+------------------+--+--------------------+->
       +-> order-by-clause -+  +-> offset-clause -+  +-> limit-to-clause -+