TRUNC

This function sets the last 3 bytes of a MACADDR value to zero or the last 5 bytes of a MACADDR8 value to zero.

TRUNC(macaddr | macaddr8)

where macaddr and macaddr8 are either columns or expressions with those data types or literal values in a valid format. Literal values must be preceded with the MACADDR or MACADDR8 keyword.

For example:

premdb=# \d ips
     Table "public.ips"
 Column |   Type   | Modifiers
--------+----------+-----------
 c1     | ipv4     |
 c2     | ipv6     |
 c3     | macaddr  |
 c4     | macaddr8 |

Distribution: Hash (c1)

premdb=# select c3, c4 from ips;
       c3         |           c4
-------------------+-------------------------
 10:20:30:40:00:00 | 10:20:30:40:00:00:00:00
(1 row)

premdb=# select trunc(c3), trunc(c4) from ips;
      trunc       |          trunc
-------------------+-------------------------
 10:20:30:00:00:00 | 10:20:30:00:00:00:00:00
(1 row)

premdb=# select trunc(macaddr '10:20:30:00:00:00') from sys.const;
      trunc
-------------------
 10:20:30:00:00:00
(1 row)

premdb=# select trunc(macaddr8 '10:20:30:00:00:00:00:00') from sys.const;
         trunc
-------------------------
 10:20:30:00:00:00:00:00
(1 row)