MySQL Forums
Forum List  »  Newbie

Re: Noob query issue
Posted by: laptop alias
Date: January 05, 2011 07:30AM

No need to apologise, just follow the instructions.

Sometimes they disappear, in which case see A.

--
Frequent responses

A. Read the Stickies at the top of the forum. Sometimes they disappear, in which case...

If your question concerns tables and data:

Within [ code ][ /code ] tags (leave off the spaces)...
1. Provide CREATE TABLE statements for each of the relevant tables
2. Provide a small but representative dataset for each of the tables, as a set of INSERT statements
3. Provide the resultset you'd expect from your query.
4. Provide the result of SELECT VERSION();

B. Group-wise Max queries
One frequently asked question relates to finding the Top-N of an aggregated result, one of a set of so-called 'GROUP-WISE MAX' queries.
Various solutions to this problem are provided at the following links:
dev.mysql.com/doc/refman/5.0/en/example-maximum-column-group-row.html
www.artfulsoftware.com/infotree/queries.php?&bw=1179#101
jan.kneschke.de/projects/mysql/groupwise-max

C. Pivot Tables
A second frequently asked question involves the transposition of rows to columns, often involving the aggregation of data, so-called 'Pivot Table' queries. Although my preferred solution is to handle the transposition at the application level, e.g. with a bit of PHP, there is excellent discussion on this topic at www.artfulsoftware.com/infotree/queries.php?&bw=1179#523.

D. Hierarchical Data
A third frequently asked question relates to handling recursion in connection with hierarchical data.
Choices include, but are not limited to, the following:
- Join the table to itself as many times as could possibly be required
- Handle the recursion at the application level, e.g. with a PHP loop <-- my preference
- Use a Stored Procedure to handle the recursion
- Switch to a Nested Set (or some sort of hybrid model) instead of the 'so-called' Adjacency List model

All of these solutions are discussed more thoroughly elsewhere, including a number of excellent, popular, and hence easily googled, articles on Hierarchical data and MySQL.

Options: ReplyQuote


Subject
Written By
Posted
January 05, 2011 06:46AM
January 05, 2011 07:04AM
January 05, 2011 07:24AM
Re: Noob query issue
January 05, 2011 07:30AM
January 05, 2011 08:01AM
January 05, 2011 08:19AM
January 05, 2011 08:26AM
January 05, 2011 09:11AM
January 05, 2011 10:41AM
January 05, 2011 09:41AM
January 05, 2011 10:40AM


Sorry, you can't reply to this topic. It has been closed.

Content reproduced on this site is the property of the respective copyright holders. It is not reviewed in advance by Oracle and does not necessarily represent the opinion of Oracle or any other party.