MySQL & nested set: slow JOIN (not using index)

Question

I have two tables:

localities:

CREATE TABLE `localities` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(100) NOT NULL,
  `type` varchar(3         


        

Answer 1

Ah, it just occurred to me.

Since you are asking for everything in the table, mysql decides to use a full table scan instead, as it deems it more efficient.

In order to get some key usage, add in some filters to restrict looking for every row in all the tables anyways.

Updating Answer:

Your second query does not make sense. You are left joining to lca yet you have a filter in it, this negates the left join by itself. Also you're looking for data in the last step of the query, meaning you will have to look through all of lt, lc and lca in order to find your data. Also you have no index with left-most column 'type' on locations, so you still need a full table scan to find your data.

If you had some sample data and example of what you are trying to achieve it would perhaps be easier to help.