Since your tables all have identical structures, if they are MYISAM type tables you could use a MERGE type table. To do this, create yet another table also with the same structure, but make its type MERGE instead MYISAM. eg: CREATE TABLE new_table_name ( ... same data structure ... ) TYPE = MERGE UNION = (table1, table2, table3, table4) INSERT_METHOD = [NO, FIRST, or LAST]; # ***
***optional declaration to forbid INSERTs or to determine which table to make INSERTs into
A SELECT query to this table will query all the constituent tables in the UNION.
MERGE type tables also support DELETE, UPDATE and INSERT. When you find duplicates, a DELETE query to the MERGE table would DELETE from all the tables, then you could reINSERT into one of them.