SSRS表达式-获取最近一个星期六的日期

Question

I am trying to find an SSRS expression that will return the date of the most recent Saturday. If the expression runs on a Saturday, I want it to display the Saturday of the previous week.

I toyed around with an example I found online, and got it to produce the value I need it to produce. Listed below:

=IIf(Parameters!O_endDate.Value = nothing, DateAdd("d", -7-(WeekDay(Today(),7))+8, Today()), Parameters!O_endDate.Value)

I apologize for the stupid post. I cannot understand why the above expression is producing the value I need, and I want to know if it will continue to work as I want it to work, when run on other days of the week in the future. Note: I ran this code on a Sunday.

Answer 1

For your purposes, I don't think you need the IIF statement - this just returns the value of the parameter if it is not nothing.

This leaves the key operation as DateAdd("d", -7-(WeekDay(Today(),7))+8, Today()) .

What this does is add -7-(WeekDay(Today(),7))+8 days to today - this can be simplified to 1-(WeekDay(Today(),7)) since -7+8=1.

Looking at the documentation here , the return_type appears to be invalid since the function is only defined for values of 1, 2 & 3 - if its working now then it may not continue to work.

This will work all the time DateAdd("d", 1 - WeekDay(Today(), 1), Today()) if you want the most recent Sunday to be today when today is a Sunday or use DateAdd("d", WeekDay(Today(), 2)), Today()) if the most recent Sunday is last week when today is a Sunday.

Note that in both cases this may produce the wrong answer at around midnight due to the 2 calls to Today() a few miliseconds apart. To be absolutely correct it should be:

Declare @DateToCheck datetime=Today()
Select DateAdd('d', 1 - WeekDay(@DateToCheck, 1), @DateToCheck) 

Answer 2

This is a more generalised approach that should be closer to ANSI SQL.

See the SQL Fiddle for SQL Server 2008.

Becuase the return value of DATEPART depends on a global database setting, the return value is adjusted for a known Saturday. By changing this to another day of the week you will get the last that day.

Answer 3

您可以尝试以下操作： =DateAdd("d", -1 * (weekday(today()) mod 7 ), today())