its better to have a unique key at least on one of the tables, but if not you have to:
1- get the results from table 1
2- get results from table 2
3- store both results in a new table and remove the duplicates.
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if not possible:
you may try this: "long way"
DELETE FROM table_X1 AS T1
WHERE EXISTS
(
SELECT 1 FROM table_X2 AS T2
WHERE T2.Fieldname = T1.Fieldname
AND T2.Fieldname = T1.Fieldname
AND T2.Fieldname = T1.Fieldname
AND T2.Fieldname = T1.Fieldname
)
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hope it will work with you :)