Find last matching result using "read table with key" - abap

Question

I need to find the sy-tabix of a the last entry in an internal table that matches v_key = x. I'm trying to do it with:
read table i_tab with key v_key = x
But since there are multiple entries in the table that match v_key = x, how can I make sure I get the sy-tabix of the last matching entry? I can't search by another key unfortunately.

Answer 1

READ TABLE is for reading single lines, for more lines you have to use LOOP:
LOOP AT itab
ASSIGNING ...
WHERE vkey EQ x.
ENDLOOP.
Right after the LOOP sy-tabix will contain the last line, where the condition is true.
As it was pointed (see discussion below), for the best performance there has to exist a NON-UNIQUE SORTED key (either primary or secondary) for this field

Answer 2

Another possibility, which is useful if you have many lines with the same v_key value.
First, make sure a line exists for X. If it's not found, then no need to pursue.
Calculate the next possible value (variable x_next_value) of the searched value (variable X). Examples:
If X is an integer, simply search X + 1. Example: for value 5, x_next_value will be 6.
If X are characters (C or string), then get the number of the last character (cl_abap_conv_**out**_ce=>uccpi), add 1, and update the last character (cl_abap_conv_**in**_ce=>uccpi).
Same kind of logic for other types of X.
Make sure your table is sorted (with preference to a table declared sorted table of ... with non-unique key v_key)
Then do READ TABLE itab WITH KEY v_key = x_next_value.
Important : even if no line is found, SY-TABIX will be set to the number of next line after all the lines having v_key = x (cf ABAP documentation of READ TABLE - Possible values for SY-SUBRC and SY-TABIX)
Pseudo code :
READ TABLE ... WITH KEY v_key = x_next_value.
" eventually BINARY SEARCH if itab is STANDARD instead of SORTED
CASE sy-subrc.
WHEN 0.
last_tabix_of_x = sy-tabix.
WHEN 4.
last_tabix_of_x = sy-tabix - 1.
WHEN 8.
last_tabix_of_x = lines( itab ).
ENDCASE.
Note : exactly two READ TABLE are needed to find the last matching result.

Answer 3

I think fastest way is
Sort itab by key.
read table itab with key key = v_key
binary search.
loop at itab assign <fs> from sy-tabix.
if <fs>-key ne v_key.
exit.
endif.
endloop.

Answer 4

I am writing a different solution which might be helpful to you.
add one column keyno in table i_tab.
When you are inserting records in table i_tab, and there are multiple records to append in table i_tab for same key, you can add keyno for each records where same key has multiple records.
For Example:
Insertion of records in Table i_tab
i_tab_line-key = 'X'.
i_tab_line-keyno = 1.
APPEND i_tab_line to i_tab.
i_tab_line-key = 'X'.
i_tab_line-keyno = 2.
APPEND i_tab_line to i_tab.
i_tab_line-key = 'X'.
i_tab_line-keyno = 3.
APPEND i_tab_line to i_tab.
Table i_tab Sorting by Key Keyno descending.
SORT i_tab by key keyno Desc.
Now Read Table will find last matching entry from table i_tab for the key.
read table i_tab with key = X
regards,
Umar Abdullah

Answer 5

sort i_tab by v_key .
read table i_tab with key v_key = x binary search.
while i_tab-key = x
lv_tabix = sy-tabix + 1 .
read table i_tab index = lv_tabix .
endwhile.
result = lv_tabix -1 .