\(\newcommand{\B}[1]{ {\bf #1} }\) \(\newcommand{\R}[1]{ {\rm #1} }\) \(\newcommand{\W}[1]{ \; #1 \; }\)
node_table#
View page sourceThe Node Table#
Discussion#
The node table defines a graph that is a tree by specifying
the parent for each node.
The node table has the following columns:
node_id#
This column has type integer and is the primary key for this table.
Its initial value is zero, and it increments by one for each row.
node_name#
This column has type text and has a different value for every row;
i.e., the names are unique and can act as substitutes for the primary key.
The names are intended to be easier for a human to remember than the ids.
parent#
This column has type integer and is the node_id
of the parent for this node.
If this node has no parents, parent is null .
Note that this is a value for the primary key in this table, but
the name of this column does not follow the
foreign key naming convention.
Children#
The children for node p is the sent of node_id values such that the corresponding parent is equal to p .
Descendant#
The set of descendants for a node p is the set children of p , grand children of p , … .
Example#
The file node_table.py
contains an example node table.