【mysql】mysql分别按年/月/日/周分组统计数据

1.统计

我们可以使用date_format()函数格式化时间，然后进行分组操作

例如有一个学生表，结构如下

-- 按年
select date_format(create_time, '%Y') years,avg(age),count(gender) from student where create_time > "2022-01-01 00:00:00" and create_time < "2022-07-19 19:58:03" group by years;
-- 按月
select date_format(create_time, '%Y-%m') months,avg(age),count(gender) from student where create_time > "2022-01-01 00:00:00" and create_time < "2022-07-19 19:58:03" group by months;
-- 按周
select date_format(create_time, '%Y-%u') weeks,avg(age),count(gender) from student where create_time > "2022-01-01 00:00:00" and create_time < "2022-07-19 19:58:03" group by weeks;
-- 按日
select date_format(create_time, '%Y-%m-%d') days,avg(age),count(gender) from student where create_time > "2022-01-01 00:00:00" and create_time < "2022-07-19 19:58:03" group by days;

如果不想用date_format函数，可以使用对应的year()/month()/week()/day()函数替代

2.占位符

date_format()需要传入一个特定的占位符，mysql常用的占位符可参考下表