MYSQL Add working days to date

问题

I want to add 5 days to the provided date, but the calculation must skip weekends.

I already know how to add 5 days without skipping weekends:

SELECT DATE_ADD(`date_field`, INTERVAL 5 DAY) As FinalDate
FROM `table_name`;

Now I want the returned value to skip weekends.

Currently if date_field = 2016-07-22 the results will be 2016-07-27
But I want the results to be 2016-07-29

回答1:

Try this:

SELECT DATE_ADD(
    date_field,
    INTERVAL 5 + 
    IF(
        (WEEK(date_field) <> WEEK(DATE_ADD(date_field, INTERVAL 5 DAY)))
        OR (WEEKDAY(DATE_ADD(date_field, INTERVAL 5 DAY)) IN (5, 6)),
        2,
        0)
    DAY
    ) AS FinalDate
FROM `table_name`;

How it works:

Firstly, it will add 5 days on your date.
Secondly, when date_field and 5 days later are in two different weeks, it must be added additional 2 days.
Thirdly, when 5 days later is Sat or Sun, it must be added additional 2 days.

回答2:

I did try your solution but faced a problem when using it with a larger interval (e.g 20 days). It works perfectly with little intervals though.

Example : for '2017-10-04' + 20 days, your algorithm return '2017-10-26'. It should be '2017-11-01' since we skip 4 weekends.

The numbers of days you add isn't calculated depending on the difference between the 2 week #, so the maximum days you can add is 2 and in my case, it should be 8 (4x2).

I modified your code to end up with this (I also add variables, much more convenient to modify)

SELECT 
@ID:='2017-10-04' as initial_date, -- the initial date in the right format to manipulate (add x day)
@DTA:=20 as days_to_add, -- number of days to add
@DA:= DATE_ADD(@ID, INTERVAL @DTA DAY) as date_add,
@LASTDAY := WEEKDAY(@DA) as last_day, -- the day (Monday, Tuesday...) corresponding to the initial date + number of days to add
@WEEK1 := DATE_FORMAT(@ID, '%v') as initial_date_week, -- format the initial date to match week mode 3 (Monday 1-53)
@WEEK2 := DATE_FORMAT(@DA, '%v') as added_date_week_nbr, -- the week # of the initial_date + number of days to add
@WEEKDIFF := @WEEK2 - @WEEK1 as week_difference, -- the difference between week 2 and week 1
DATE_ADD(@ID,
        INTERVAL @DTA + 
            if ( @WEEKDIFF > 0 or @LASTDAY in (5,6),
              2,
              0
              ) + 
             if (@WEEKDIFF > 1,
             @WEEKDIFF*2,
             0
             ) DAY
    ) AS FinalDate

The way I get my week numbers can seems weird but this is because I'm running this in France and my DB seems to be configured in a way that weeks are natively starting by Sunday, "%v" represent the 'mode 3' for weeks, you can check the MySQL documentation here for more details : https://dev.mysql.com/doc/refman/5.7/en/date-and-time-functions.html (ctrl + F > '%v')

I didn't implement the public holiday yet, but I'm thinking of adding X days in the calculation each times one of this day is in the period we're looking at.

According to my (few) tests, this should work. Let me know if not

回答3:

try this out, should work nicely, basically loop through each of the days and check if they are saturday or sunday, ignore them.

https://social.technet.microsoft.com/wiki/contents/articles/30877.t-sql-extending-dateadd-function-to-skip-weekend-days.aspx

回答4:

Plus hollydays 1 or 2

select GREATEST(WEEKDAY(NOW()) - 4, 0) 'hollydays'

回答5:

WHERE datefield BETWEEN CURRENT_DATE AND CURRENT_DATE + INTERVAL 7 DAY
AND WEEKDAY(datefield) NOT IN (5,6);

来源：https://stackoverflow.com/questions/38522170/mysql-add-working-days-to-date

标签

mysql

sql

dateinterval