Обсуждение: daisychain rows to detect value
I have a table of network ports. These ports are part of something, be it a cabinet patch panel, or a network switch. np_connects_to references a hardware ID, which can be the cabinet, switch,router etc. containing the port. no_port is the name of the port. np_untagged_vlan is the VLAN ID for the port, with NULL being allowed. Each port can then be patched to another port. For example: np_connects_to | np_port | np_patch_to | np_patch_port | np_untagged_vlan ---------------+---------+-------------+---------------+----------------- 1 | 01 | | | 1 2 | 23B | 1 | 01 | 3 | 23A | 2 | 23B | Row 1 shows a switch port set to VLAN 1. Row 2 shows a port in cabiner 'A' (Panel B port 23) which is patched to the switch port. Row 3 shows a port in cabinet 'B' (Panel A port 23) which is the other end cabinet A port 23B Is there a way to be able to propogate the untagged VLAN to any port patched to it? -- https://fundraise.cancerresearchuk.org/page/garys-march-march
Is there a way to be able to propogate the untagged VLAN to any port patched
to it?
PostgreSQL natively provides a Recursive CTE capability that can be used to solve arbitrary depth hierarchy problems.
Triggers are useful if you want to do the calculation during writes instead of during reads.
David J.