How does MySQL count the number of different value bars in a field?

Statistics of different values in time span, number of occurrences at that time
, here I want to find out the number of different values in the periods field for each month within 1 years.
For example in the visible 201 May-April, periods 2 appeared 3 times, 3 appeared 1 times, the most critical is periods you do not know how many possible values, perhaps this month 1, perhaps not.

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Statistics of different values in time span, number of occurrences at that time
, here I want to find out the number of different values in the periods field for each month within 1 years.
For example in the visible 201 May-April, periods 2 appeared 3 times, 3 appeared 1 times, the most critical is periods you do not know how many possible values, perhaps this month 1, perhaps not.

Wrote a demo, online preview

First, the time format I use is date, 年-月-日 this form

Number of statistics,count再group by 列名

SELECT `periods`,DATE_FORMAT(time,'%Y-%m') as month,COUNT(*) AS `times` FROM `product` GROUP BY `periods`,`month` ORDER BY `month` DESC

DOC:
Date_format:http://www.w3school.com.cn/sql/func_date_format.asp
Group By:http://www.w3school.com.cn/sql/sql_groupby.asp

With the Count function

You can use two group by conditions.

select count(id), periods, from_unixtime(time, '%Y-%m')from productwhere  你的条件group by periods,from_unixtime(time, '%Y-%m')

Well, that's probably the way it looks.

Select Periods,sum (periods) as count from product where month>= ' time ' and mouth<= ' time ' GROUP by periods

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