nodes()

Read(280) Label: child node,

Here’s how to use nodes() function.

P.nodes()

Description:

Find records in a recursive way where the foreign key values reference a specified record.

Syntax:

P.nodes(F,r,n)

Note:

r. The function finds all records from record sequence P where foreigh key F references record r, the root node, in a recursive way. The resulting records are record r’s child nodes. If these child nodes don’t have any child nodes, that is, their foreign key values don’t reference them, they are called the root node’s leaf nodes; otherwise they are called the subtrees.

If the specified record r can’t be found, the function will return NULL. Parameter n is the maximum recursion depth, whose default is 1,000.

Parameters:

P

A record sequence

F

Field name

r

A record

n

A number

Options:

@d

Make the function return leaf-level nodes.

@p

Make the function return all child nodes and their level relative to the root node.

Return value:

A sequence

Example:

 

A

 

1

=file("D://emp.txt").import@t().keys(empid)

 

2

>A1.switch(mgrid,A1:empid)

 

3

=A1.nodes(mgrid,A1.select@1(name=="Diana"),5)

According to mgrid field, the foreign key references, search for all records of Diana’s subordinates and those of the subordinates of Diana’s subordinates

4

=A1.nodes@d(mgrid,A1.select@1(name=="Diana"),5)

Search for the records of Diana’s subordinates who are not a manager

5

=A1.nodes@p(mgrid,A1.select@1(name=="Diana"),5)

 

Display a relationship structure with Diana as the root, from which you see that Diana is the manager of empid=7, who is the manager of empid=14