Hi,
FOR ALL ENTRIES is like :
LOOP AT IT_A.
SELECT *
APPENDING TABLE IT_B
FROM B
WHERE TOTO = IT_A-TOTO
AND TITI = IT_A-TITI
ENDLOOP.
If you need to know prerequisites ask the trans. ABAPDOCU it all explains better than what we could try to say here.
Just be careful about the problem with identical result, SAP will give you only one entries (it's also explain in the documentation)
And, don't forget, FOR ALL ENTRIES is not really good for performance, if you have less than 3.000 entries prefer the RANGES
regards
Fred