Mysql按年份和计数分组字段

Question

For example, I have a table like this:

|  id  |  name  |  register_date  |  gender  |

|1     |John    |2011-02-02       |man       |
|2     |Jane    |2011-02-02       |woman     |
|3     |Jihn    |2012-04-04       |man       |
|4     |Jeni    |2012-02-02       |woman     |
|5     |Joni    |2012-02-02       |woman     |

How is the query to create this result from that table above?

|  RegisterYear  |  man  |  woman  |

|2011            |   1   |    1    |
|2012            |   1   |    2    |

Answer 1

Group by the year and sum each gender

select year(register_date) as registeryear,
       sum(gender = 'man') as man,
       sum(gender = 'woman') as woman       
from your_table
group by registeryear

Answer 2

Here you go:

SELECT YEAR(register_date) as RegisterYear,
       SUM(gender = 'man') as man,
       SUM(gender = 'woman') as woman
from register 
group by RegisterYear;

SQLFiddle Demo

Output:

REGISTERYEAR    MAN     WOMAN
===================================
2011            1       1
2012            1       2