1  RSE
      The record selection expression (RSE) is used in many statements
      to specify a set of records, called a record stream. The format
      is:
   
          [FIRST n]
          [       ] [context-variable-1 IN]    rse-source-1
          [  ALL  ]
   
            [CROSS [context-variable-2 IN] rse-source-2 [OVER field-name-1]
   
        [WITH Boolean-expression]  [REDUCED to reduce-key[,...]]
   
        [SORTED BY {sort-key} [,...]]]
   
      The format for rse-source is:
   
           { remote-domain-name                                            }
           { rdb-relation-name                                             }
           { rdb-domain-name                                               }
           { rms-domain-name                                               }
           { collection-name                                               }
           { list                                                          }
           {                                                               }
           { dbms-record-name   [ { MEMBER }                            ]  }
           {                    [ { OWNER  } [OF] [context-var.set-name]]  }
           { dbms-domain-name   [ { WITHIN }                            ]  }
    
   
2  Arguments
    
   
   context-variable
   
      a variable name used with the records identified by the rse.
    
   
   rse-source
   
      the name of a readied domain or established collection. An rse
      source must be specified.
    
   
   field-name-1
   
      the name of the field specified in rse-source-1 and rse-source-2.
    
   
   boolean-expression
   
      a specification of the conditions a record must meet to be
      included in the record stream.
    
   
   reduce-key
   
      a list of one or more reduce keys (see HELP REDUCE).
    
   
   sort-key
   
      a list of one or more sort keys (see HELP SORT).
    
   
   remote-domain-name
   
      the name of any remote domain.
    
   
   rdb-relation-name
   
      the name of the relation that is the source for the rse.
    
   
   rdb-domain-name
   
      the name of the relational domain that is the source for the rse.
    
   
   rms-domain-name
   
      the name of the RMS domain that is the source for the rse.
    
   
   collection-name
   
      the name of a DEC DATATRIEVE collection that is the source for
      the rse.
    
   
   list
   
      the name of a DEC DATATRIEVE list that is the source for the rse.
    
   
   Oracle CODASYL DBMS-record-name
   
      the name of the Oracle CODASYL DBMS record that is the source for
      the rse.
    
   
   Oracle CODASYL DBMS-domain-name
   
      the name of the Oracle CODASYL DBMS domain that is the source for
      the rse.
    
   
   set-name
   
      the name of a Oracle CODASYL DBMS set. The record type of the rse
      must be a participant in that set.
   
      The CROSS clause lets you make the cross product of one or more
      domains. If you specify the OVER clause, DEC DATATRIEVE finds
      the specified field in each domain and only returns the combined
      records if the fields are identical. For more details on CROSS
      see HELP CROSS. For complete information on the record selection
      expression see the DEC DATATRIEVE Reference Manual.
    
   
2  Examples
      An RSE can be simply:
   
      o  A record source:
   
          YACHTS
          CURRENT
          A
   
      o  A record source with a Boolean expression and a SORTED BY
         clause:
   
         YACHTS  WITH PRICE GT 0  SORTED BY LOA
   
      o  A record source with a Boolean expression, REDUCED TO clause,
         and a SORTED BY clause:
   
         YACHTS  WITH PRICE GT 0  REDUCED TO TYPE, LOA SORTED BY LOA
   
      o  Multiple record sources with a common field:
   
         YACHTS CROSS OWNERS OVER TYPE
   
      o  Multiple record sources with context variables:
   
         A IN YACHTS CROSS B IN OWNERS OVER BUILDER WITH A.MODEL NE B.MODEL