Calculate time difference between timestamps in milliseconds

Used the below sql to calculate the difference in timestamps in milliseconds.

select TX_ID,

       extract(hour   from (END_TIMESTAMP - START_TIMESTAMP)) * 3600000

        + extract(minute from (END_TIMESTAMP - START_TIMESTAMP)) * 60000

        + extract(second from (END_TIMESTAMP - START_TIMESTAMP)) * 1000 diff_im_ms

from t_transaction

where TX_ID IN (6587728628,6587728639,6587728647);

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