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Left Join between two large tables too slow!!
Posted by: Rupinder Dhaliwal
Date: July 01, 2013 04:56AM

We have 2 large tables having below structure:

CREATE TABLE Table1 (
`proid` bigint(20) NOT NULL,
`total` bigint(20) NOT NULL DEFAULT '0',
`create_date_time` datetime NOT NULL,
`site` varchar(255) DEFAULT NULL,
`exp` varchar(255) DEFAULT NULL,
KEY `pr_id` (`proid`),
KEY `pr_created_at` (`create_date_time`),
KEY `pr_site` (`site`),
KEY `pr_exp` (`exp`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE Table2 (
`proid` bigint(20) NOT NULL,
`total` bigint(20) NOT NULL DEFAULT '0',
`create_date_time` datetime NOT NULL,
`site` varchar(255) DEFAULT NULL,
`exp` varchar(255) DEFAULT NULL,
KEY `pr_id` (`proid`),
KEY `pr_created_at` (`create_date_time`),
KEY `pr_siter` (`site`) ,
KEY `pr_exp` (`exp`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


Both the above tables have 18000+ records.

We're trying to fetch the data from the above two tables uing left join as below:

select
*
from
(select create_date_time,site,exp, sum(total) as imp_total
from Table2
group by create_date_time,site,exp) as imp
inner join
(select create_date_time,site,exp, sum(total) as req_total
from Table1
group by create_date_time,site,exp) as pr
on
imp.site=pr.site
and imp.create_date_time = pr.create_date_time
and imp.exp=pr.exp;

The requirement is that we need to group the data in tables by all three columns create_date_time,site and exp. Also there has to be a left join to fetch data from both tables.

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Left Join between two large tables too slow!!
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July 01, 2013 04:56AM


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