[DOCS] I notice Postgresql 'HAVING' doesn't work.

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Page: https://www.postgresql.org/docs/9.5/static/tutorial-agg.html
Description:

Following this tutorial The Nested Set Model on
http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/
  

Section: Depth of a Sub-Tree.
SELECT node.name, (COUNT(parent.name) - (sub_tree.depth + 1)) AS depth
FROM nested_category AS node,
        nested_category AS parent,
        nested_category AS sub_parent,
        (
                SELECT node.name, (COUNT(parent.name) - 1) AS depth
                FROM nested_category AS node,
                nested_category AS parent
                WHERE node.lft BETWEEN parent.lft AND parent.rgt
                AND node.name = 'PORTABLE ELECTRONICS'
                GROUP BY node.name, node.lft
                ORDER BY node.lft
        )AS sub_tree
WHERE node.lft BETWEEN parent.lft AND parent.rgt
        AND node.lft BETWEEN sub_parent.lft AND sub_parent.rgt
        AND sub_parent.name = sub_tree.name
GROUP BY node.name, node.lft, sub_tree.depth
ORDER BY node.lft;
+----------------------+---------+
| name                 |   depth |
|----------------------+---------|
| PORTABLE ELECTRONICS |       0 |
| MP3 PLAYERS          |       1 |
| FLASH                |       2 |
| CD PLAYERS           |       1 |
| 2 WAY RADIOS         |       1 |
+----------------------+---------+


Section: Find the Immediate Subordinates of a Node.
SELECT node.name, (COUNT(parent.name) - (sub_tree.depth + 1)) AS depth
FROM nested_category AS node,
        nested_category AS parent,
        nested_category AS sub_parent,
        (
                SELECT node.name, (COUNT(parent.name) - 1) AS depth
                FROM nested_category AS node,
                nested_category AS parent
                WHERE node.lft BETWEEN parent.lft AND parent.rgt
                AND node.name = 'PORTABLE ELECTRONICS'
                GROUP BY node.name, node.lft
                ORDER BY node.lft
        )AS sub_tree
WHERE node.lft BETWEEN parent.lft AND parent.rgt
        AND node.lft BETWEEN sub_parent.lft AND sub_parent.rgt
        AND sub_parent.name = sub_tree.name
GROUP BY node.name, node.lft, sub_tree.depth
HAVING depth <= 1
ORDER BY node.lft;
Adding 'HAVING depth <= 1' to the query still return the same results as
above instead of this:
+----------------------+---------+
| name                 |   depth |
|----------------------+---------|
| PORTABLE ELECTRONICS |       0 |
| MP3 PLAYERS          |       1 |
| FLASH                |       1 |
| CD PLAYERS           |       1 |
| 2 WAY RADIOS         |       1 |
+----------------------+---------+


NOTE: I edited the query by add node.lft, sub_tree.depth to the GROUP BY.

I don't know if I'm doing anything wrong?