資料庫的常見操作

資料庫日期操作

1. 查詢各學生的年齡，只按年份來算

-- mysql 寫法一:

select sid,sname,
year
(now()
)-year
(sage) 年齡 from student
-- mysql 寫法二:
select sid,sname,date_format(
now(),
'%y'
)-date_format(sage,
'%y'
) 年齡 from student
-- mysql 寫法三:
select sname,
left
(now()
,4)-
left
(sage,
4) 年齡 from student

-- mysql寫法三 

select sname, timestampdiff(
year
, sage,
now())
as age from student

select

*from
(select
*,date_sub(curdate(),
interval weekday(curdate())
day) firstdayofweek
, concat_ws(
'-',
year
(curdate())
,date_format(sage,
'%m-%d'
)) thisyear
,concat_ws(
'-',
year
(curdate())
+1,date_format(sage,
'%m-%d'
)) nextyear
,date_add(curdate(),
interval
6-weekday(curdate())
day) lastdayofweek
from student
) t1
where
thisyear>= firstdayofweek and thisyear<=lastdayofweek
ornextyear>= firstdayofweek and nextyear<=lastdayofweek

select

*from
(select
*,date_add(curdate(),
interval
7-weekday(curdate())
day) firstdayofnextweek
, concat_ws(
'-',
year
(curdate())
,date_format(sage,
'%m-%d'
)) thisyearbirthday
,concat_ws(
'-',
year
(curdate())
+1,date_format(sage,
'%m-%d'
)) nextyearbirthday
,date_add(curdate(),
interval
13-weekday(curdate())
day) lastdayofnextweek
from student
) t1
where
thisyearbirthday>= firstdayofnextweek and thisyearbirthday<=lastdayofnextweek
ornextyearbirthday>= firstdayofnextweek and nextyearbirthday<=lastdayofnextweek

-- mysql寫法一：

select sid,sname,sage,date_format(sage,
'%m'
),date_format(
now(),
'%m'
)from student where date_format(sage,
'%m'
)=date_format(
now(),
'%m'
)-- mysql寫法二：
select sid,sname,sage,
month
(now()
),month
(sage) 月份 from student where
month
(now()
)=month
(sage)
-- mysql寫法三：
select
*from student where substr(sage,6,
2)=substr(curdate(),
6,2)

注意:要考慮下個月跨年的情況

select s.sid,s.sname,s.sage,t1.nextmonth

from student s,
(select
case
when date_format(
now(),
'%m'
)<
12then date_format(
now(),
'%m')+
1else
1end nextmonth
) t1
where date_format(s.sage,
'%m'
)=t1.nextmonth

select

*from
(select
*,curdate(
) today 
,concat_ws(
'-',
year
(curdate())
,date_format(sage,
'%m-%d'
)) thisyearbirthday
,concat_ws(
'-',
year
(curdate())
+1,date_format(sage,
'%m-%d'
)) nextyearbirthday
,date_add(curdate(),
interval
6day
) lastday
from student
) t1
where
thisyearbirthday>=today and thisyearbirthday<=lastday
ornextyearbirthday>= today and nextyearbirthday<=lastday

select

*from
(select
*,curdate(
) today 
,concat_ws(
'-',
year
(curdate())
,date_format(sage,
'%m-%d'
)) thisyearbirthday
,concat_ws(
'-',
year
(curdate())
+1,date_format(sage,
'%m-%d'
)) nextyearbirthday
,date_add(curdate(),
interval
29day
) lastday
from student
) t1
where
thisyearbirthday>=today and thisyearbirthday<=lastday
ornextyearbirthday>= today and nextyearbirthday<=lastday

select sid,sname,sage,

month
(sage) 月,
day(sage) 日 from student where
month
(now()
)=month
(sage)
andday
(now()
)=day(sage)

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