# Defining the parent/child relationship v16

To determine the children for any given row:

Evaluate

`parent_expr`

on the given row.Evaluate

`child_expr`

on any other row resulting from the evaluation of`table_expression`

.If

`parent_expr = child_expr`

, then this row is a child node of the given parent row.Repeat the process for all remaining rows in

`table_expression`

. All rows that satisfy the equation in step 3 are the children nodes of the given parent row.

##### Note

The evaluation process to determine if a row is a child node occurs on every row returned by `table_expression`

before the `WHERE`

clause is applied to `table_expression`

.

Iteratively repeating this process, treating each child node found in the prior steps as a parent, constructs an inverted tree of nodes. The process is complete when the final set of child nodes has no children of its own. These are the leaf nodes.

A `SELECT`

command that includes a `CONNECT BY`

clause typically includes the `START WITH`

clause. The `START WITH`

clause determines the rows that are to be the root nodes, that is, the rows that are the initial parent nodes upon which to apply the algorithm.