1.MySQL 的 YEARWEEK 是获取年份和周数的一个函数，函数形式为 YEARWEEK(date[,mode])
例如 2010-3-14 ，礼拜天
SELECT YEARWEEK('2010-3-14') 返回 11
SELECT YEARWEEK('2010-3-14',1) 返回 10
其中第二个参数是 mode ，具体指的意思如下：
| Mode | First day of week | Range | Week 1 is the first week … |
| 0 | Sunday | 0-53 | with a Sunday in this year |
| 1 | Monday | 0-53 | with more than 3 days this year |
| 2 | Sunday | 1-53 | with a Sunday in this year |
| 3 | Monday | 1-53 | with more than 3 days this year |
| 4 | Sunday | 0-53 | with more than 3 days this year |
| 5 | Monday | 0-53 | with a Monday in this year |
| 6 | Sunday | 1-53 | with more than 3 days this year |
| 7 | Monday | 1-53 | with a Monday in this year |
2. weekofyear函数是计算出当前日期所在周数，和YEARWEEK('日期',1)的周数一致，但YEARWEEK('日期',1)在小于10的时候，不带0
select WEEKOFYEAR('2016-2-2'); =5