Syntax:
FROM_UNIXTIME(unix_timestamp), FROM_UNIXTIME(unix_timestamp,format)

Returns a representation of the unix_timestamp argument as a value in
'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS format, depending on whether
the function is used in a string or numeric context. unix_timestamp is
an internal timestamp value such as is produced by the UNIX_TIMESTAMP()
function.

If format is given, the result is formatted according to the format
string, which is used the same way as listed in the entry for the
DATE_FORMAT() function.
