READ TABLE with dynamic key fields? - dynamic

Question

I have the name of a table DATA lv_tablename TYPE tabname VALUE 'xxxxx', and a generic FIELD-SYMBOLS: <lt_table> TYPE ANY TABLE. which contains entries selected from that corresponding table.
I've defined my line structure FIELD-SYMBOLS: <ls_line> TYPE ANY. which i'd use for reading from the table.
Is there a way to create a READ statement on <lt_table> fully specifying the key fields?
I am aware of the statement / addition READ TABLE xxxx WITH KEY (lv_field_name) = 'asdf'., but this however wouldn't work (afaik) for a dynamic number of key fields, and I wouldn't like to create a large number of READ TABLE statements with an increasing number of key field specifications.
Can this be done?

Answer 1

Actually i found this to work
DATA lt_bseg TYPE TABLE OF bseg.
DATA ls_bseg TYPE bseg.
DATA lv_string1 TYPE string.
DATA lv_string2 TYPE string.
lv_string1 = ` `.
lv_string2 = lv_string1.
SELECT whatever FROM wherever INTO TABLE lt_bseg.
READ TABLE lt_bseg INTO ls_bseg
WITH KEY ('MANDT') = 800
(' ') = ''
('BUKRS') = '0005'
('BELNR') = '0100000000'
('GJAHR') = 2005
('BUZEI') = '002'
('') = ''
(' ') = ''
(' ') = ' '
(lv_string1) = '1'
(lv_string2) = ''.
By using this syntax one can just specify as many key fields as required. If some fields will be empty, then these will just get ignored, even if values are specified for these empty fields.
One must pay attention that using this exact syntax (static definitions), 2 fields with the exact same name (even blank names) will not be allowed.
As shown with the variables lv_string1 and lv_string2, at run-time this is no problem.
And lastly, one can specify the fields in any order (i don't know what performance benefits or penalties one might get while using this syntax)

Answer 2

There seems to be the possibility ( like a dynamic select statement whith binding and lt_dynwhere ).
Please refer to this post, there was someone, who also asked for the requirement:
http://scn.sap.com/thread/1789520

Answer 3

3 ways:
READ TABLE itab WITH [TABLE] KEY (comp1) = value1 (comp2) = value2 ...
You can define a dynamic number of key fields by indicating statically the maximum number of key fields in the code, and indicate at runtime some empty key field names if there are less key fields to be used.
LOOP AT itab WHERE (where) (see Addition 4 "WHERE (cond_syntax)")
Available since ABAP 7.02.
SELECT ... FROM #itab WHERE (where) ...
Available since ABAP 7.52. It may be slow if the condition is complex and cannot be handled by the ABAP kernel, i.e. it needs to be executed by the database. In that case, only few databases are supported (I think only HANA is supported currently).
Examples (ASSERT statements are used here to prove that the conditions are true, otherwise the program would fail):
TYPES: BEGIN OF ty_table_line,
key_name_1 TYPE i,
key_name_2 TYPE i,
attr TYPE c LENGTH 1,
END OF ty_table_line,
ty_internal_table TYPE SORTED TABLE OF ty_table_line WITH UNIQUE KEY key_name_1 key_name_2.
DATA(itab) = VALUE ty_internal_table( ( key_name_1 = 1 key_name_2 = 1 attr = 'A' )
( key_name_1 = 1 key_name_2 = 2 attr = 'B' ) ).
"------------------ READ TABLE
DATA(key_name_1) = 'KEY_NAME_1'.
DATA(key_name_2) = 'KEY_NAME_2'.
READ TABLE itab WITH TABLE KEY
(key_name_1) = 1
(key_name_2) = 2
ASSIGNING FIELD-SYMBOL(<line>).
ASSERT <line> = VALUE ty_table_line( key_name_1 = 1 key_name_2 = 2 attr = 'B' ).
key_name_2 = ''. " ignore this key field
READ TABLE itab WITH TABLE KEY
(key_name_1) = 1
(key_name_2) = 2 "<=== will be ignored
ASSIGNING FIELD-SYMBOL(<line_2>).
ASSERT <line_2> = VALUE ty_table_line( key_name_1 = 1 key_name_2 = 1 attr = 'A' ).
"------------------ LOOP AT
DATA(where) = 'key_name_1 = 1 and key_name_2 = 1'.
LOOP AT itab ASSIGNING FIELD-SYMBOL(<line_3>)
WHERE (where).
EXIT.
ENDLOOP.
ASSERT <line_3> = VALUE ty_table_line( key_name_1 = 1 key_name_2 = 1 attr = 'A' ).
"---------------- SELECT ... FROM #itab
SELECT SINGLE * FROM #itab WHERE (where) INTO #DATA(line_3).
ASSERT line_3 = VALUE ty_table_line( key_name_1 = 1 key_name_2 = 1 attr = 'A' ).