nleft and nright Catalog arguments ?

[Joe Germann]

What are the nleft and nright arguments in the Catalog table used for? How are their values determined?

Thanks,

Joe

 

[usermar]

In the ps_category table each category has a numeric field nleft and nright. This field represents the location of this category with respect to the rest of the categories, it is like a node in the category tree that is recalculated every time a category is created or moved.

In my case currently I have the problem that each category that I create or move is created with nleft and nright value "0" which means that its taxonomy is not represented correctly in the front office.
https://www.prestashop.com/forums/topic/1063628-nleft-nright-with-value-0-in-ps_category-when-creating-new-categories/

[Joe Germann]

4 hours ago, usermar said:

In the ps_category table each category has a numeric field nleft and nright. This field represents the location of this category with respect to the rest of the categories, it is like a node in the category tree that is recalculated every time a category is created or moved.

In my case currently I have the problem that each category that I create or move is created with nleft and nright value "0" which means that its taxonomy is not represented correctly in the front office.
https://www.prestashop.com/forums/topic/1063628-nleft-nright-with-value-0-in-ps_category-when-creating-new-categories/

Interesting.  I make a category by using an ODBC connection to the database and then fill in the fields for Category, Category_Lang, Category_Shop, etc.   So my questions comes down to this:  What is the actual algorithm for defining nleft and nright values?