I guess t1id in table1 and t2id in table2 is primary key for corrosponding tables.
if so the you can use following approach -
1) as you want to delete from both the tables, you need to store the t1id (or t2id) into one temp table so that you can use the values for deleting second table
2) for extracting the desired t1id/t2id you need to group the joined table with T1name, Data1, Data2, Data3 and select the record where you are getting multiple records.
3) Exclude only one t1id from duplicate records found for delete.
so for this you can use some commands like shown below -
CREATE TABLE test_table
as (SELECT T1id
FROM Table1, Table2
WHERE T1name, Data1, Data2,
Data3 IN (SELECT T1name, Data1, Data2, Data3
FROM (SELECT T1name, Data1, Data2, Data3, COUNT(*)
FROM Table1, Table2
WHERE T1id = T2id
GROUP BY T1name, Data1, Data2, Data3
HAVING COUNT(*) > 1))
AND T1id NOT IN (SELECT MIN(T1id)
FROM Table1, Table2
WHERE T1id = T2id
GROUP BY T1name, Data1, Data2, Data3));
DELETE FROM Table1 WHERE T1id IN (SELECT T1id FROM Test_Table);
DELETE FROM Table2 WHERE T2id IN (SELECT T1id FROM Test_Table);
COMMIT;
Drop TABLE Test_Table;