# 9.12. 網路位址函式及運算子

[Table 9.36](https://www.postgresql.org/docs/10/static/functions-net.html#cidr-inet-operators-table)shows the operators available for the`cidr`and`inet`types. The operators`<<`,`<<=`,`>>`,`>>=`, and`&&`test for subnet inclusion. They consider only the network parts of the two addresses (ignoring any host part) and determine whether one network is identical to or a subnet of the other.

\*\*Table 9.36. \*\*`cidr`**and**`inet`**Operators**

| Operator | Description                 | Example                                         |                      |                    |
| -------- | --------------------------- | ----------------------------------------------- | -------------------- | ------------------ |
| `<`      | is less than                | `inet '192.168.1.5' < inet '192.168.1.6'`       |                      |                    |
| `<=`     | is less than or equal       | `inet '192.168.1.5' <= inet '192.168.1.5'`      |                      |                    |
| `=`      | equals                      | `inet '192.168.1.5' = inet '192.168.1.5'`       |                      |                    |
| `>=`     | is greater or equal         | `inet '192.168.1.5' >= inet '192.168.1.5'`      |                      |                    |
| `>`      | is greater than             | `inet '192.168.1.5' > inet '192.168.1.4'`       |                      |                    |
| `<>`     | is not equal                | `inet '192.168.1.5' <> inet '192.168.1.4'`      |                      |                    |
| `<<`     | is contained by             | `inet '192.168.1.5' << inet '192.168.1/24'`     |                      |                    |
| `<<=`    | is contained by or equals   | `inet '192.168.1/24' <<= inet '192.168.1/24'`   |                      |                    |
| `>>`     | contains                    | `inet '192.168.1/24' >> inet '192.168.1.5'`     |                      |                    |
| `>>=`    | contains or equals          | `inet '192.168.1/24' >>= inet '192.168.1/24'`   |                      |                    |
| `&&`     | contains or is contained by | `inet '192.168.1/24' && inet '192.168.1.80/28'` |                      |                    |
| `~`      | bitwise NOT                 | `~ inet '192.168.1.6'`                          |                      |                    |
| `&`      | bitwise AND                 | `inet '192.168.1.6' & inet '0.0.0.255'`         |                      |                    |
| \`       | \`                          | bitwise OR                                      | \`inet '192.168.1.6' | inet '0.0.0.255'\` |
| `+`      | addition                    | `inet '192.168.1.6' + 25`                       |                      |                    |
| `-`      | subtraction                 | `inet '192.168.1.43' - 36`                      |                      |                    |
| `-`      | subtraction                 | `inet '192.168.1.43' - inet '192.168.1.19'`     |                      |                    |

[Table 9.37](https://www.postgresql.org/docs/10/static/functions-net.html#cidr-inet-functions-table)shows the functions available for use with the`cidr`and`inet`types. The`abbrev`,`host`, and`text`functions are primarily intended to offer alternative display formats.

\*\*Table 9.37. \*\*`cidr`**and**`inet`**Functions**

| Function                        | Return Type | Description                                                    | Example                                          | Result             |
| ------------------------------- | ----------- | -------------------------------------------------------------- | ------------------------------------------------ | ------------------ |
| `abbrev(inet`)                  | `text`      | abbreviated display format as text                             | `abbrev(inet '10.1.0.0/16')`                     | `10.1.0.0/16`      |
| `abbrev(cidr`)                  | `text`      | abbreviated display format as text                             | `abbrev(cidr '10.1.0.0/16')`                     | `10.1/16`          |
| `broadcast(inet`)               | `inet`      | broadcast address for network                                  | `broadcast('192.168.1.5/24')`                    | `192.168.1.255/24` |
| `family(inet`)                  | `int`       | extract family of address;`4`for IPv4,`6`for IPv6              | `family('::1')`                                  | `6`                |
| `host(inet`)                    | `text`      | extract IP address as text                                     | `host('192.168.1.5/24')`                         | `192.168.1.5`      |
| `hostmask(inet`)                | `inet`      | construct host mask for network                                | `hostmask('192.168.23.20/30')`                   | `0.0.0.3`          |
| `masklen(inet`)                 | `int`       | extract netmask length                                         | `masklen('192.168.1.5/24')`                      | `24`               |
| `netmask(inet`)                 | `inet`      | construct netmask for network                                  | `netmask('192.168.1.5/24')`                      | `255.255.255.0`    |
| `network(inet`)                 | `cidr`      | extract network part of address                                | `network('192.168.1.5/24')`                      | `192.168.1.0/24`   |
| `set_masklen(inet`,`int`)       | `inet`      | set netmask length for`inet`value                              | `set_masklen('192.168.1.5/24', 16)`              | `192.168.1.5/16`   |
| `set_masklen(cidr`,`int`)       | `cidr`      | set netmask length for`cidr`value                              | `set_masklen('192.168.1.0/24'::cidr, 16)`        | `192.168.0.0/16`   |
| `text(inet`)                    | `text`      | extract IP address and netmask length as text                  | `text(inet '192.168.1.5')`                       | `192.168.1.5/32`   |
| `inet_same_family(inet`,`inet`) | `boolean`   | are the addresses from the same family?                        | `inet_same_family('192.168.1.5/24', '::1')`      | `false`            |
| `inet_merge(inet`,`inet`)       | `cidr`      | the smallest network which includes both of the given networks | `inet_merge('192.168.1.5/24', '192.168.2.5/24')` | `192.168.0.0/22`   |

Any`cidr`value can be cast to`inet`implicitly or explicitly; therefore, the functions shown above as operating on`inet`also work on`cidr`values. (Where there are separate functions for`inet`and`cidr`, it is because the behavior should be different for the two cases.) Also, it is permitted to cast an`inet`value to`cidr`. When this is done, any bits to the right of the netmask are silently zeroed to create a valid`cidr`value. In addition, you can cast a text value to`inet`or`cidr`using normal casting syntax: for example,`inet(expression`)or`colname`::cidr.

[Table 9.38](https://www.postgresql.org/docs/10/static/functions-net.html#macaddr-functions-table)shows the functions available for use with the`macaddr`type. The function`trunc(macaddr`)returns a MAC address with the last 3 bytes set to zero. This can be used to associate the remaining prefix with a manufacturer.

\*\*Table 9.38. \*\*`macaddr`**Functions**

| Function         | Return Type | Description              | Example                              | Result              |
| ---------------- | ----------- | ------------------------ | ------------------------------------ | ------------------- |
| `trunc(macaddr`) | `macaddr`   | set last 3 bytes to zero | `trunc(macaddr '12:34:56:78:90:ab')` | `12:34:56:00:00:00` |

The`macaddr`type also supports the standard relational operators (`>`,`<=`, etc.) for lexicographical ordering, and the bitwise arithmetic operators (`~`,`&`and`|`) for NOT, AND and OR.

[Table 9.39](https://www.postgresql.org/docs/10/static/functions-net.html#macaddr8-functions-table)shows the functions available for use with the`macaddr8`type. The function`trunc(macaddr8`)returns a MAC address with the last 5 bytes set to zero. This can be used to associate the remaining prefix with a manufacturer.

\*\*Table 9.39. \*\*`macaddr8`**Functions**

| Function                     | Return Type | Description                                                                         | Example                                          | Result                    |
| ---------------------------- | ----------- | ----------------------------------------------------------------------------------- | ------------------------------------------------ | ------------------------- |
| `trunc(macaddr8`)            | `macaddr8`  | set last 5 bytes to zero                                                            | `trunc(macaddr8 '12:34:56:78:90:ab:cd:ef')`      | `12:34:56:00:00:00:00:00` |
| `macaddr8_set7bit(macaddr8`) | `macaddr8`  | set 7th bit to one, also known as modified EUI-64, for inclusion in an IPv6 address | `macaddr8_set7bit(macaddr8 '00:34:56:ab:cd:ef')` | `02:34:56:ff:fe:ab:cd:ef` |

The`macaddr8`type also supports the standard relational operators (`>`,`<=`, etc.) for ordering, and the bitwise arithmetic operators (`~`,`&`and`|`) for NOT, AND and OR.