Articles tagged with sql

1. MySQL Multiple-Column Indexes: Order Matters

   Posted on May 18, 2011 in Programming

   This will just be a short reminder. If you're planning to create multiple-column indexes in MySQL, remember that the order of the columns matters. As the MySQL documentation points out, any "leftmost prefix of the index can be used." This means that the index can be used for any number …

2. Django Debug Toolbar Multiple Database Support

   Posted on October 23, 2010 in Programming

   Django Debug Toolbar (DjDT) is a must-have tool for most Django developers (at least the ones I know!). One of the most useful features of DjDT is the SQL Debug Panel that displays information about SQL queries including execute time and EXPLAIN output.

   As of version 0.8.3, Django …

3. MySQL: Query caused different errors on master and slave

   Posted on August 14, 2010 in System Administration

   We ran across the following error on a MySQL slave server recent:

   mysql> SHOW SLAVE STATUS \G
   <snip>
   Last_Error: Query caused different errors on master and slave. Error on master: 'Deadlock found when trying to get lock; try restarting transaction' (1213), Error on slave: 'no error' (0). Default database: '<database_name …

4. Listing WordPress Database Queries

   Posted on August 12, 2010 in Programming

   If you need to debug what queries your WordPress site is making, try adding the following PHP to your theme:

   <?php
     foreach ( $wpdb->queries as $query ) {
       echo "$query[0]<br />";
     }
   ?>
   

   For this code to work, you need to add the following line to wp-config.php:

   define('SAVEQUERIES', true);
   

   After that …

5. Two Random Asterisk-Related SQL Queries

   Posted on July 15, 2010 in voice

   I hate losing useful SQL queries, so I tend to save them. Ever so often, I stumble across a file of queries from some work I was doing months ago. The following two queries are just such a case. I was analyzing some call data for a call center that …

6. ActiveRecord and SELECT DISTINCT

   Posted on November 20, 2007 in Programming

   I'm writing this post for two reasons:

   1. For some reason, I couldn't find a lot of information on ActiveRecord and SELECT DISTINCT().
   2. I'm hoping some Ruby / ActiveRecord guru will stumble across this and provide a better solution.

   Recently, I was working on a project written in Ruby with ActiveRecord that …

7. Logging Active Record Queries to a File

   Posted on October 29, 2007 in Programming

   I was recently helping a developer with some SQL optimizations in Ruby. The developer was using Active Record, and (until now) my Active Record experience has been pretty minimal.

   One thing that was really driving me bonkers was how to get Active Record to print out the queries it was …