MySQL Toad result set filter and compare features

When you work daily in a data warehouse environment, you will inevitably compare or filter or summarize data for further analysis or debugging.  The result set shown in MySQL Toad 4.5 has couple of very nice features that will help you compare or filter the results quickly - right in the "Results" pane.  In the picture below I was calculating Herfindahl Index for a group of AdWords accounts.  The query resulted in date, some daily metric  and its index; and if I am further interested in filtering for specific range of index, for example, I can point the mouse at  Herfindahl_Index column and click on "filter" icon. See below.

Also, by comparing the data between two result sets, the data comparison feature avoids bringing data to Excel or running sub-queries.  For example, I modified the original query and ran it again and wanted to quickly see for any difference in numbers between two results sets at date level, which I could by just doing the data comparison between result 7 & 8 below.  I know I have couple of ways of comparing the data as noted above, but being able to compare in Result set pane was the quickest - didn't need to modify the query nor move the data.

Finally, you can use Pivot & Chart by dragging and dropping the columns to the grid area.  For small data sets this is handy.

Hope that helps,
Shiva

Character set, Collation

Here is an interesting challenge that I ran into in the Data Warehouse environment. While debugging a particular business user query, I joined between a string built in a sub-query to a column in a particular fact table with some 20million rows. BTW, I was using MySQL 5.0 and Toad 4.5 to run this query and instead of getting any result I got the following error!

MySQL Database Error: Illegal mix of collations (utf8_general_ci,COERCIBLE) and (latin1_swedish_ci,IMPLICIT) for operation '='    22    0

The query was simple and similar to

SELECT s.str, s.d1, s.d2
FROM (
    SELECT distinct 'string' str, dimension1 d1, dimension 2 d2
    FROM table_1
    WHERE ...
) s
LEFT OUTER JOIN table_2 t2
ON ...
WHERE s.str = t2.str
AND ...

Introduction and using MySQL Explain

Like in any database query optimization is critical for MySQL data warehouse environment and having a better understanding of the "Explain plan" helps the database application developer avoiding issues with query  performance. Also, DBAs will like your queries and they would be more than happy to help you optimize them.

MySQL's "Explain" statement provides details on query parsing and execution steps and outputs 10 fields -
id, select_type, table, type, possible_keys, key, key_len, ref, rows and Extra columns.

You run the statement by issuing

explain <sql query> #-- Insert your query between < and >. 

Shown below is the Toad's output of explain plan of a self-joined table's query with where clause. The table has around 20million rows. The query took less than 0.6seconds to index through ~70K rows and with "const" and a func (date_add function) to compare between one days data to its previous day data.

SELECT a.ad_date, a.unit_id, a.max_cpc, 
               SUM(coalesce(a.max_cpc, a.max_cpc) - coalesce(b.max_cpc, a.max_cpc)) diff_cpc
       FROM  sem_kw_summary a
       LEFT JOIN  sem_kw_summary b
           ON  date_add(a.ad_date, INTERVAL -1 day)  = b.ad_date
           AND a.unit_id = b.unit_id
       WHERE date_add(CURRENT_DATE, INTERVAL -1 day) = a.ad_date
         AND a.engine = 'google'
       GROUP BY a.ad_date,  a.unit_id