SELECT FROM_UNIXTIME(FLOOR(EPOCH_TIMESTAMP/1000)) FROM table; --if milliseconds
SELECT FROM_UNIXTIME(FLOOR(EPOCH_TIMESTAMP)) FROM table; --no milliseconds
#--------------------------------SQL SERVER----------------------------------
#use this to convert forom bigint unix to datetime
#replace 1500123123 with your number
select DATEADD(second,1500123123, CAST('1970-01-01 00:00:00' AS datetime))
#it's way better to put this in a function and call the function