INSERT OR REPLACE INTO + SELECT as source in Oracle
Table1: A (DATA1, DATA2, DATA3) 
Table2: B (DATA1, DATA2, DATA3)

Assumption: First fieldName of both table is primary key

MERGE INTO A TA 
    USING (SELECT * FROM B) TB 
    ON (TA.DATA1 = TB.DATA1) 
    WHEN NOT MATCHED THEN INSERT (TA.DATA1, TA.DATA2, TA.DATA3) 
      VALUES (TB.DATA1, TB.DATA2, TB.DATA3);