SQL statement challenge - easy or difficult? : mysql, category, database, sql

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7.8

SQL statement challenge - easy or difficult?

Asked by ibell in MySQL Server

Tags: mysql, category, database, sql

I'm coming over from Oracle to MySQL and under Oracle we could do things like: SELECT * from x where y IN (select * from z) .. I am not sure this can be done with MySQL so I'm posing a scenario here and inquiring as to how you MySQL programmers would handle it. It's pretty basic - it's more a design thing but it all revolves around the database query.

Given two tables:

notes:
id autoincrement int primary
catid int
...

categories:
id autoincrement int primary
parentid int
...

a record in the note table would correspond to a category and have an id associated with it. Pretty basic, but the idea behind the categories is to make them nested. So a list of categories might go like this:

colors (id: 1, parentid: 0)
dark colors (id:2 parentid: 1)
brown (id:3 parentid: 2)
black (id:4 parentid: 2)
light colors (id: 4 parentid: 1)
yellow (id: 6 parentid: 4)
pink (id: 7 parentid: 4)

The trick is, given a category ID, to extract rows from "notes" with that category ID and the id of any subcategories under it in the category table.

Can this be done in a single, MySQL statement?

For example, using the above category layout, if I wanted to pull all rows from notes with category id 1, it would pull everything with category ids from 1-7; if I selected category 2, it would pull records from notes with the category id 2,3 and 4. If category 6 was selected, only records with that category id would be pulled since it has no sub-categories. Kind of the scheme that you might see used under Yahoo or eBay's directories.

Assuming that there may be more than 3 levels, what's the best way to handle such a query that would be most efficient?

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20091111-EE-VQP-92

SQL statement challenge - easy or difficult?

Asked by ibell in MySQL Server

Tags: mysql, category, database, sql

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