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Internal Tables, Grouping with FOR, Nesting

This example demonstrates nested control level processing using GROUP BY in a FOR expression.

Other versions: 7.31 | 7.40 | 7.54

Source Code

    TYPES: BEGIN OF group,
             fldate   TYPE sflight-fldate,
             seatsocc TYPE sflight-seatsocc,
           END OF group,
           group_tab type STANDARD TABLE OF group WITH EMPTY KEY.

    DATA: sflight_tab TYPE SORTED TABLE OF sflight
                      WITH UNIQUE KEY carrid connid fldate.

    DATA(display_members) = abap_false.
    cl_demo_input=>request( EXPORTING text  = `Display Group Members?`
                            CHANGING  field = display_members ).

    DATA(out) = cl_demo_output=>new( ).

    SELECT *
           FROM sflight
           INTO TABLE @sflight_tab.

    DATA(total_sum) =
      REDUCE i(
        LET wg = xsdbool( to_upper( display_members ) = abap_true ) IN
        INIT t = 0
             o = out
        FOR GROUPS OF carrid_group IN sflight_tab
              GROUP BY carrid_group-carrid
        LET carrid_sum =
          REDUCE i(
            INIT s1 = 0
                 o1 = out
            FOR GROUPS OF connid_group IN GROUP carrid_group
                  GROUP BY connid_group-connid
            LET connid_sum =
              REDUCE i(
                INIT s2 = 0
                FOR m IN GROUP connid_group
                NEXT s2 = s2 + m-seatsocc )
                o2 = out->next_section(
                    |{ connid_group-carrid } { connid_group-connid }| )
                o3 = COND #( WHEN wg = abap_true
                               THEN LET group = VALUE group_tab(
                                FOR m IN GROUP connid_group
                                  ( CORRESPONDING #( m ) ) ) IN
                                    out->write( group ) ) IN
            NEXT s1 = s1 + connid_sum
                 o1 = o1->write( |Sum: { connid_sum }| ) ) IN
        NEXT t = t + carrid_sum
             o = o->line(
                  )->write( |Carrier Sum: { carrid_sum }|
                  )->line( ) ).

    out->write( |Overall Sum: | &&
                |{ total_sum }| )->display( ).

Description

This example works in the same way as the corresponding example for LOOP AT ... GROUP BY, but uses the expression FOR GROUPS ... OF for table reductions with REDUCE instead of the group loops. In both cases, the group keys after GROUP BY are constructed in exactly the same way. Instead of the member loops, further table reductions and a table comprehension are used here.