与MSSQL相比，MySQL Join查询速度较慢

Question

I have the following simple join query

SELECT
  count(*) 
FROM 
  DBx.caseview p2015
  INNER JOIN DBy.caseview p2014 ON p2015.casenumber=p2014.casenumber;

For some reason it just leaves MySQL hanging there for a lot of time until I get tired and cancel it. On the contrary, if run exactly the same code on MSSQL with the same data set the query takes a few seconds at most.

Is there a parameter that needs to be changed on MySQL to speed up this type of queries?

Here's my table in MySQL

CREATE TABLE `caseview` (
  `ID` bigint(20) NOT NULL AUTO_INCREMENT,
  `CASEID` varchar(18) DEFAULT NULL,
  `CASENUMBER` int(10) DEFAULT NULL,
  `ACCOUNTID` varchar(18) DEFAULT NULL,
  `ACCOUNT` varchar(256) DEFAULT NULL,
  `ASSETID` varchar(18) DEFAULT NULL,
  `SAPPRODUCTGROUP` varchar(10) DEFAULT NULL,
  `PRODUCT` varchar(128) DEFAULT NULL,
  `FAMILY` varchar(128) DEFAULT NULL,
  `CONTACTID` varchar(18) DEFAULT NULL,
  `OWNERID` varchar(18) DEFAULT NULL,
  `TYPE` varchar(128) DEFAULT NULL,
  `PRIORITY` varchar(24) DEFAULT NULL,
  `ORIGIN` varchar(24) DEFAULT NULL,
  `SUBJECT` varchar(256) DEFAULT NULL,
  `STATUS` varchar(24) DEFAULT NULL,
  `LASTACTIVITY` varchar(1024) DEFAULT NULL,
  `INITALDESCRIPTION` varchar(1024) DEFAULT NULL,
  `CLOSEDDATE` datetime DEFAULT NULL,
  `CREATEDDATE` datetime DEFAULT NULL,
  `LASTMODIFIEDDATE` datetime DEFAULT NULL,
  PRIMARY KEY (`ID`),
  UNIQUE KEY `ID_UNIQUE` (`ID`)
) ENGINE=InnoDB AUTO_INCREMENT=122393 DEFAULT CHARSET=utf8;

There's two tables with exactly the same configuration as above, just different data

DBx.caseview p2015 has 197647 rows DBy.caseview p2014 has 122392 rows

Answer 1

Create an Index for CASENUMBER field.

ALTER TABLE `caseview` ADD INDEX ( `CASENUMBER` ) ;

Give it a few seconds to create the index and run the query again.