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The Table Editor Table Field Application
This application edits the Person table in the Personnel database. It is a forms application that allows the user to update a person's values, remove the person, or add new persons. Various table field utilities are provided with the application to demonstrate how they work.
The objects used in this application are:
The program's database environment.
A table in the database, with three columns:
    name (char(20))
    age (smallint)
    number (integer)
Number is unique.
The VIFRED form with a single table field.
A table field in the form, with two columns:
    name (char(20))
    age (integer)
When initialized, the table field includes the hidden column number (integer).
At the beginning of the application, the program opens a database cursor to load the table field with data from the Person table. After loading the table field, the user can browse and edit the displayed values. The user can add, update, or delete entries. When finished, the values are unloaded from the table field and, in a multi-statement transaction, the updates are transferred back into the Person table.
Sample Application
-- I/O utilities
with text_io; use text_io;

exec sql include sqlca;

exec sql declare person table
   (name     char(20),        -- Person name
    age      smallint,        -- Age
    number   integer);        -- Unique id number
procedure Table_Edit is
      exec sql begin declare section;
          -- Table field row states
          type Row_States is (
              row_undef,      -- Empty or undefined row
              row_new,        -- Appended by user
              row_unchange,  -- Loaded by program, but not updated
              row_change,     -- Loaded by program and updated
              row_delete      -- Deleted by program
          not_found: constant := 100; -- SQLCA value for no rows
          -- Person information corresponds to "person" table
          pname:   String(1..20);  -- Full name
          page:    Short_Integer;  -- Age
          pnumber: Integer;        -- Unique person number
          pmaxid:  Integer;        -- Maximum person id number
          -- Table field entry information
          state: Row_States;       -- State of data set row
          recnum,                  -- Record number
          lastrow: Integer;        -- Last row in table field
          -- Utility buffers
          search:  String(1..20);  -- Name to find in search loop
          password: String(1..13); -- Password buffer
          msgbuf:  String(1..100); -- Message buffer
          respbuf: String(1..1);   -- Response buffer
      exec sql end declare section;

      -- Error handling variables for database updates
      update_error: Boolean; -- Error in updates?
      update_commit: Boolean; -- Commit updates
      -- Load the information from the "person" table into the
      -- person variables. Also, save the maximum person id
      -- number.

      function Load_Table return Integer is
           exec sql begin declare section;
                  -- Person information
                  pname:   String(1..20); -- Full name
                  page:    Short_Integer; -- Age
                  pnumber: Integer;        -- Unique person number
                  maxid:   Integer;    -- Maximum person id number
            exec sql end declare section;
            exec sql declare loadtab cursor for
                  select name, age, number
                  from person;

            -- Set up error handling for loading procedure
            exec sql whenever sqlerror goto Load_End;
            exec sql whenever not found goto Load_End;

      begin                      -- Load_Table
            exec frs message 'Loading Person Information . . .';

            -- Fetch the maximum person id number for later use
            exec sql select max(number)
                  into :maxid
                  from person;

            exec sql open loadtab;

            while (sqlca.sqlcode = 0) loop
                -- Fetch data into record and load table field
                exec sql fetch loadtab into
                                :pname, :page, :pnumber;

                exec frs loadtable personfrm persontbl
                      (name = :pname, age = :page,
                                   number = :pnumber);
            end loop;

          exec sql whenever sqlerror continue;
          exec sql close loadtab;

          return maxid;
      end Load_Table;

begin -- Table_Edit
      -- Set up error handling for main program
      exec sql whenever sqlwarning continue;
      exec sql whenever not found continue;
      exec sql whenever sqlerror STOP;

      -- Start up Ingres and the FORMS system
      exec sql connect 'personnel';

      exec frs forms;

      -- Verify that the user can edit the "person" table
      exec frs prompt noecho ('Password for table editor: ',
      if (password /= "MASTER_OF_ALL") then
          exec frs message 'No permission for task.
                                        Exiting . . .';
          exec frs endforms;
          exec sql disconnect;
      end if;

      exec frs message 'Initializing Person Form . . .';
      exec frs forminit personfrm;

      -- Initialize "persontbl" table field with a data set
      -- in FILL mode, so that the runtime user can append rows.
      -- To keep track of events occurring to original
      -- rows loaded into the table field, hide the unique
      -- person number.

      exec frs inittable personfrm persontbl FILL
                        (number = integer);

      pmaxid := Load_Table;

      -- Display the form and allow runtime editing
      exec frs display personfrm update;
      exec frs initialize;
      exec frs begin;
          -- Provide menu items, as well as the system FRS
          -- key, to scroll to both extremes of the table field.
          exec frs scroll personfrm persontbl to 1;
      exec frs end;

      exec frs activate menuitem 'Top';
      exec frs begin;
          exec frs scroll personfrm persontbl TO 1; -- Backward
      exec frs end;

      exec frs activate menuitem 'Bottom';
          exec frs begin;
          exec frs scroll personfrm persontbl to end; -- Forward
      exec frs end;

      exec frs activate menuitem 'Remove';
      exec frs begin;
          -- Remove the person in the row the user's cursor
          -- is on. If there are no persons, exit operation
          -- with message. Note that this check cannot
          -- really happen, as there is always at least one
          -- UNDEFINED row in FILL mode.

          exec frs inquire_frs table personfrm
              (:lastrow = lastrow(persontbl));
          if (lastrow = 0) then
              exec frs message 'Nobody to Remove';
              exec frs sleep 2;
              exec frs resume field persontbl;
          end if;

      exec frs deleterow personfrm persontbl;  -- Recorded for
                                               -- later
      exec frs end;

      exec frs activate menuitem 'Find';
      exec frs begin;
          -- Scroll user to the requested table field entry.
          -- Prompt the user for a name, and if one is typed
          -- in, loop through the data set searching for it.

          search := (1..20 => ' ');
              exec frs prompt ('Person''s name : ', :search);
          if (search(1) = ' ') then
              exec frs resume field persontbl;
          end if;

              exec frs unloadtable personfrm persontbl
                   (:pname = name, :recnum = _record,
                    :state = _state);
              exec frs begin;
                  -- Do not compare with deleted rows
                 if (state /= ROW_DELETE and pname = search) then
                   exec frs scroll personfrm persontbl TO :recnum;
                      exec frs resume field persontbl;
                  end if;
           exec frs end;

          -- Fell out of loop without finding name. Issue error.
          msgbuf := (1..100 => ' ');
          msgbuf(1..62) := "Person '" & search &
                "' not found in table [HIT RETURN] ";
          exec frs prompt noecho (:msgbuf, :respbuf);
      exec frs end;

      exec frs activate menuitem 'Exit';
      exec frs begin;
          exec frs validate field persontbl;
          exec frs breakdisplay;
      exec frs end;
      exec frs finalize;

    -- Exit person table editor and unload the table field.
    -- If any updates, deletions or additions were made,
    -- duplicate these changes in the source table. If the
    -- user added new people, assign a unique id to each person
    -- before adding the person to the table. To do this,
    -- increment the previously-saved maximum id number with
    -- each insert.
    -- Do all the updates in a multi-statement transaction
    exec sql savepoint savept;

    update_commit := TRUE;

    -- Hard code the error handling in the UNLOADTABLE loop,
    -- so as to cleanly exit the loop.

    exec sql whenever sqlerror continue;

    exec frs message 'Exiting Person Application . . .';

    exec frs unloadtable personfrm persontbl
        (:pname = name, :page = age,
         :pnumber = number, :state = _state);
    exec frs begin;

        case (state) is
            when row_new =>
                -- Filled by user. Insert with new unique id.
                pmaxid := pmaxid + 1;
                exec sql insert into person (name, age, number)
                   values (:pname, :page, :pmaxid);

            when row_change =>
                -- Updated by user. Reflect in table.
                exec sql update person set
                    name = :pname, age = :page
                    where number = :pnumber;

            when row_delete =>
                -- Deleted by user, so delete from table.
                -- Note that only original rows, not rows
                -- appended at runtime, are saved by the
                -- program.
                exec sql delete from person
                    where number = :pnumber;

            when others =>
                -- Else UNDEFINED or UNCHANGED -
                -- No updates required.
        end case;

        -- Handle error conditions -
        -- If an error occurred, abort the transaction.
        -- If no rows were updated, inform user and
        -- prompt for continuation.
        if (sqlca.sqlcode < 0) then -- Error
            exec sql inquire_sql (:msgbuf = errortext);
            exec sql rollback to savept;
            update_error := TRUE;
            update_commit := FALSE;
            exec frs endloop;
        elsif (sqlca.sqlcode = NOT_FOUND) then
            msgbuf := (1..100 => ' ');
            msgbuf(1..62) :=
                "Person '" & pname &
                "' not updated. Abort all updates? ";
            exec frs prompt noecho (:msgbuf, :respbuf);
            if (respbuf = "Y" or respbuf = "y") then
                update_commit := FALSE;
                exec sql rollback to savept;
                exec frs endloop;
            end if;
        end if;
    exec frs end;
    if (update_commit) then
        exec sql commit;               -- Commit the updates
    end if;

    exec frs endforms; -- Terminate FORMS and Ingres
    exec sql disconnect;

    if (update_error) then
       put_line( "Your updates were aborted because of error:" );
        put_line( msgbuf );
    end if;

end Table_Edit;
Last modified date: 06/10/2024