Comments on: How to optimize subqueries and joins in MySQL http://www.xaprb.com/blog/2006/04/30/how-to-optimize-subqueries-and-joins-in-mysql/ Stay curious! Thu, 09 Feb 2012 09:56:43 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Jamie Hamel-Smith http://www.xaprb.com/blog/2006/04/30/how-to-optimize-subqueries-and-joins-in-mysql/#comment-19586 Jamie Hamel-Smith Sun, 21 Aug 2011 06:03:58 +0000 http://www.xaprb.com/blog/?p=127#comment-19586 You sir are my new hero! I'm a self taught developer at a web company and your advice just got a query I'd been writing for a cron job from 235 seconds down to 2 seconds. Nesting of the subquery is almost magical in the right situation. Life-saver! You sir are my new hero! I’m a self taught developer at a web company and your advice just got a query I’d been writing for a cron job from 235 seconds down to 2 seconds.

Nesting of the subquery is almost magical in the right situation. Life-saver!

]]> By: Arpit http://www.xaprb.com/blog/2006/04/30/how-to-optimize-subqueries-and-joins-in-mysql/#comment-18986 Arpit Sat, 18 Dec 2010 02:36:31 +0000 http://www.xaprb.com/blog/?p=127#comment-18986 pls help me optimize this query..its already optimized 2 some extent..bt i want 2 c if it can get further.. SELECT e.emp_no as EMP_No,DEp.dept_name AS CurrentDEpt,e.first_nAme as FirstName,e.last_nAme as SurName,t.tiTle as CurrentStatus,e.genDer as Gender,s.salary,(s.salary/10) as BOnus FROM (dEpARTMeNts dep) JOIN (dept_emp de) ON (de.dept_no = dep.depT_NO) JOIN (employees e) ON (de.emp_no = e.emP_NO) JOIN (titles t) ON (t.emp_NO = e.emp_no AND (t.to_date = '9999-01-01')) join (salaries s) on (s.emp_no = t.emp_no and s.to_date = '9999-01-01') having s.salary >100000 order by e.emp_no pls help me optimize this query..its already optimized 2 some extent..bt i want 2 c if it can get further..

SELECT e.emp_no as EMP_No,DEp.dept_name AS CurrentDEpt,e.first_nAme as FirstName,e.last_nAme as SurName,t.tiTle as CurrentStatus,e.genDer as Gender,s.salary,(s.salary/10) as BOnus

FROM (dEpARTMeNts dep) JOIN (dept_emp de) ON (de.dept_no = dep.depT_NO) JOIN (employees e) ON (de.emp_no = e.emP_NO) JOIN (titles t) ON (t.emp_NO = e.emp_no AND (t.to_date = ’9999-01-01′))
join (salaries s) on (s.emp_no = t.emp_no and s.to_date = ’9999-01-01′) having s.salary >100000
order by e.emp_no

]]> By: nishi http://www.xaprb.com/blog/2006/04/30/how-to-optimize-subqueries-and-joins-in-mysql/#comment-18534 nishi Tue, 03 Aug 2010 15:54:05 +0000 http://www.xaprb.com/blog/?p=127#comment-18534 update tableA,tableB set tableA.col2 = 1 where tableA.col1 = tableB.col1 and (tableB.col2 200); Its taking couple of hours to execute the below query. Both tables have millions of entries and index is on col1, col2 and col3 of tableB.Also col1 in tableB is a foreign key referring to col1 of tableA What can I do to make it run fast? It will be of great help if you could help me with this asap update tableA,tableB
set tableA.col2 = 1
where tableA.col1 = tableB.col1 and (tableB.col2 200);

Its taking couple of hours to execute the below query. Both tables have millions of entries and index is on col1, col2 and col3 of tableB.Also col1 in tableB is a foreign key referring to col1 of tableA
What can I do to make it run fast?
It will be of great help if you could help me with this asap

]]> By: admin http://www.xaprb.com/blog/2006/04/30/how-to-optimize-subqueries-and-joins-in-mysql/#comment-18504 admin Thu, 15 Jul 2010 15:56:28 +0000 http://www.xaprb.com/blog/?p=127#comment-18504 I wanted to thank you for your help in suggesting the wrapper subquery trick. I had a query which took forever but now it runs pretty quick. I wanted to thank you for your help in suggesting the wrapper subquery trick. I had a query which took forever but now it runs pretty quick.

]]> By: Michael Mior http://www.xaprb.com/blog/2006/04/30/how-to-optimize-subqueries-and-joins-in-mysql/#comment-18490 Michael Mior Fri, 09 Jul 2010 02:41:40 +0000 http://www.xaprb.com/blog/?p=127#comment-18490 I know this post is ancient now. But I just wanted to thank you for your help in suggesting the wrapper subquery trick. It helped me go from a query which timed out after one hour to one which executes in around 5 seconds. Awesome! I know this post is ancient now. But I just wanted to thank you for your help in suggesting the wrapper subquery trick. It helped me go from a query which timed out after one hour to one which executes in around 5 seconds. Awesome!

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