After doing some research, it appears as if it's possible to use a SELECT subquery in the SET of an UPDATE statement. i did find some examples and here is my code, however when I click the "check" button it's saying the field (my entire select subquery) is unknown and neither in one of the specified tables or defined by a "DATA". Do I have a syntax issue or is there another reason why it's not taking this as a valid statement? Thanks for the help!
LOOP AT IT_DATA
UPDATE /BIC/AZDP_O0140
SET /BIC/ZCOUNTER = (SELECT COUNT( DISTINCT MATERIAL )
FROM /BIC/AZDP_O0140
WHERE MATERIAL EQ IT_DATA-MATERIAL
GROUP BY MATERIAL).
ENDLOOP.