Allowing the user to sort a tabular form

Question

Dear Experts,
I have several tabular forms that I want my user to be able to sort on a some of the column in the form at well, I thought of creating some buttons on the top of each of the columns and when they press on the button it sorts, do guys agree with this or is there a better way to achieve the same.
Regards.
hali

Answer 1

hi Hali,
Here you have a code sample. It's a pl/sql package you can put easily in an application library.
Calling the code
Create a non base table block with the following name convention: <block_name_to_be_sorted>_SORT
Create in this block the buttons representing de item headers. Each button must have the following name: <item_name_to_be_sorted>_SORT.
Put a call tot procedure "lib$sort.mainn_button" in when-button-pressed trigger on block level.
Set the default sort order in When-new-form-instance trigger by calling
lib$sort.mainn (<block name to be sorted>, <item_name_to_be_sorted>)"
You can also sort on non-base table items. In this case the naming convention for your header button must be: <item_to_be_sorted>_SORT_NDB.
In this case you have to create a parameter with the same name. The value of this parameter contains the expression for sorting e.g. another column value or a call to a function.
Full code:
Package header
package LIB$SORT as
PROCEDURE mainn
( p_block_name_table varchar2                     
, p_item_name_table varchar2
, p_asc_desc varchar2 default 'ASC'                    
PROCEDURE mainn_button;
end;
Package body
package body lib$sort as
procedure execute_last_query
     ( p_block                              varchar2
     )     is                                                                           
l_procedure_naam     varchar2(60) := 'lib$last_query.execute_last_query_replace';
     l_blok_id                         block := find_block (p_block);
     l_last_query          varchar2(2000);
     l_where_clause          varchar2(2000);
     l_pos_from                    number(4);
     l_pos_where                    number(4);
     l_pos_order_by          number(4);
     l_pos_string               number;
BEGIN
l_last_query := get_block_property (l_blok_id, last_query);
l_pos_from          := instr(upper(l_last_query), 'FROM');
l_pos_where     := instr(upper(l_last_query), 'WHERE' , l_pos_from);
     if nvl(l_pos_where, 0) = 0 then
          null;
     else
     l_where_clause := substr (l_last_query, l_pos_where + 5);
     l_pos_order_by     := instr(upper(l_where_clause), 'ORDER BY');
     l_where_clause := substr(l_where_clause, 1, l_pos_order_by -1);
     end if;
     go_block (p_block);
     do_key ('execute_query');
END;
FUNCTION item_to_be_sorted (p_item_name_sort varchar2) RETURN varchar2 IS
     l_item_name     varchar2(30);
BEGIN
     l_item_name := p_item_name_sort;
l_item_name := replace(l_item_name, '_SORT_NDB');
l_item_name := replace(l_item_name, '_SORT');
l_item_name := substr (l_item_name, instr(l_item_name, '.') + 1);
return (l_item_name);
END;
FUNCTION block_to_be_sorted (p_block_name_sort varchar2) RETURN varchar2 IS
     l_block_name     varchar2(30);
BEGIN
l_block_name := replace(p_block_name_sort, '_SORT');
return (l_block_name);
END;
PROCEDURE mainn ( p_block_name_table varchar2
                                        , p_item_name_table varchar2
                                   , p_asc_desc varchar2 default 'ASC'
                                        ) IS
     l_procedure_name                    varchar2(30)      := 'lib$sort';
     l_block_id_buttons                block                ;
     l_item_id_buttons                item                    ;
     l_item_id                                        item;
     l_cur_item                                   varchar2(60);
     l_cur_item_id                              item;
     cl_character_asc                    constant varchar2(1) := '>';
     cl_character_desc                    constant varchar2(1) := '<';
     l_label_cur_item                    varchar2(200);
     l_label_without_characters          varchar2(200);
     l_label                                             varchar2(200);
     l_order_by                                   varchar2(2000);
     l_basetable                                   boolean;
     l_counter                                        number(2) := 1;
     l_asc_desc                                   varchar2(4);
     l_new_label                              varchar2(200);
     l_order_by_par                         varchar2(2000);
     l_width_item                              number;
     l_block_name_buttons     varchar2(30) := p_block_name_table||'_SORT';
     l_item_name_buttons               varchar2(30) := p_item_name_table||'_SORT' ;
BEGIN
     l_block_id_buttons                := find_block (l_block_name_buttons);
     l_item_id_buttons                := find_item (l_block_name_buttons||'.'||l_item_name_buttons);
     if id_null (l_item_id_buttons) then
          -- Item not found, maybe the button sorts a non base table item
          -- In this case the name of the button ends with '_SORT_NDB'
               l_item_name_buttons := p_item_name_table||'_SORT_NDB' ;
               l_item_id_buttons      := find_item (l_block_name_buttons||'.'||l_item_name_buttons);
               if id_null (l_item_id_buttons) then
                    message ('Item '||p_item_name_table||' has no valid header. Name must be '||p_item_name_table||'_SORT'
                    ||' or '||p_item_name_table||'_SORT_NDB'
                    raise form_trigger_failure;
               else
                    l_basetable := false;
               end if;
     else
          l_basetable := true;                    
     end if;          
--Remove sort character on all buttons
l_cur_item := l_block_name_buttons|| '.' ||get_block_property(l_block_id_buttons, first_item);
while l_cur_item <> l_block_name_buttons||'.' and l_counter < 15 loop
               l_cur_item_id := find_item (l_cur_item);
          if l_cur_item = l_item_name_buttons then
                    null;
          else
               l_label_cur_item := get_item_property (l_cur_item_id, LABEL);
               l_label_without_characters := ltrim(ltrim(ltrim(l_label_cur_item, cl_character_asc), cl_character_desc));
               if l_label_without_characters = l_label_cur_item then
                    null;
               else
                    set_item_property (l_cur_item_id, LABEL, l_label_without_characters);
               end if;
end if;
-- Goto next item in block with buttons
l_cur_item      := l_block_name_buttons||'.'||get_item_property(l_cur_item_id,nextitem);
l_counter           := l_counter + 1;
     end loop;
-- Put the sort character on the right character
     l_label := get_item_property (l_item_id_buttons, LABEL);
     l_new_label := ltrim(ltrim(ltrim(l_label, cl_character_asc), cl_character_desc));
     if upper(p_asc_desc) = 'DESC' then
               l_asc_desc := 'desc';
               l_new_label := cl_character_desc||' '||l_new_label;
               set_item_property (l_item_id_buttons, label, l_new_label);
     elsif nvl(instr(l_label, cl_character_asc), 0) = 0 then
               l_asc_desc := 'asc';
               l_new_label := cl_character_asc||' '||l_new_label;
               set_item_property (l_item_id_buttons, label, l_new_label);
     else
               l_asc_desc := 'desc';
               l_new_label := cl_character_desc||' '||l_new_label;
               set_item_property (l_item_id_buttons, label, l_new_label);
     end if;
-- Perform the actual sort of the block with data
     --For a basetable item, the sort condition is the item itself
     --For a NON basetable item, the sort condition is set by a forms parameter
     if l_basetable then
          l_order_by := p_item_name_table||' '||l_asc_desc;
     else          
          l_order_by := name_in('parameter.'||p_item_name_table||'_SORT_NDB')||' '||l_asc_desc;
     end if;
     set_block_property (p_block_name_table, order_by, l_order_by);
END;
PROCEDURE mainn_button IS
     l_item varchar2(30) := name_in('system.cursor_item');
     l_block_name_buttons varchar2(30) := name_in('system.trigger_block');
     l_block_name_table varchar2(30) := block_to_be_sorted (name_in('system.trigger_block'));
     l_item_name_buttons varchar2(30) := name_in('system.trigger_item');
     l_item_name_table varchar2(30) := item_to_be_sorted (name_in('system.trigger_item'));
     l_asc_desc     varchar2(10);
BEGIN
     if get_item_property (l_item_name_buttons, label) like '>%' then
          l_asc_desc := 'DESC';
     else
          l_asc_desc := 'ASC';
     end if;
mainn(l_block_name_table, l_item_name_table, l_asc_desc);
     execute_last_query (l_block_name_table);
     go_item (l_item_name_table);
END;
end;
Regards,
Matthieu de Graaf