SELECT DISTINCT columnAAA,name,bf1.columnBBB,bf2.columnBBB
FROM table1 AS bt
LEFT JOIN table_to_join AS bf1 ON bt.columnAAA=bf1.columnCCC
LEFT JOIN table_to_join AS bf2 ON bt.columnAAA=bf2.columnDDD
INTO OUTFILE '/var/lib/mysql-files/table1.csv' FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"' LINES TERMINATED BY '\r\n';