计算Sql中日期之间的年数

Question

I need to calculate the number of complete years between two dates in sql. The query I am using currently to calculate is

--Date1 > Date2
CASE
WHEN YEAR(Date1) = YEAR(Date2)
    THEN DATEDIFF(year, Date2, Date1)
WHEN YEAR(Date1) > YEAR(Date2) 
        AND MONTH(Date1) >= MONTH(Date2)
        AND DAY(Date1) >= DAY(Date2)
    THEN DATEDIFF(year, Date2, Date1)
ELSE
    DATEDIFF(year, Date2, Date1) - 1

However I need to tweak it somehow so that it considers the time between 1/5/2011 and 30/4/2012 as 1 complete year.

Answer 1

在比较之前将一天添加到Date2 ：

dateadd(day, 1, Date2)

Answer 2

If the goal is to consider 1-year-less-a-day to be a full year, what about simply adding 1 day to your later date? dateadd() should do it.

mysql> SELECT ADDDATE('2011-05-01', INTERVAL 1 DAY);
        -> '2011-05-02'

I don't think that would cause other erroneous calculations...