一条SQL语句怎么求环比！这个月简历数减去上个月的（如图）

一条SQL语句如何求环比！这个月简历数减去上个月的（如图）

【这个月简历数】-【上个月的简历数】=【环比数】（如图）

sql语句如何写？
SELECT DATE_FORMAT(m_adddate,'%m') as month,count(m_id) as zong,DATE_FORMAT(m_adddate,'%Y') as year from job_myreceive where DATE_FORMAT(m_adddate,'%Y')=2011 GROUP BY DATE_FORMAT(m_adddate,'%m');

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------解决方案--------------------
嗯，这样写清楚些

SELECT DATE_FORMAT(a.m_adddate,'%Y%m') as Ym, count(*) as `当月`,

(select count(*) from job_myreceive where 

 DATE_FORMAT(a.m_adddate,'%Y%m') = DATE_FORMAT(DATE_add(m_adddate,INTERVAL 1 MONTH),'%Y%m')

) as 上月

 FROM job_myreceive a group by 1

Ym     当月   上月  

201012 6      0 

201101 2      6 

201105 1      0 

201107 2      0 

201112 1      0 

201305 1      0