Need to find day of week then set variable

Question

Hello all!
I'm trying to make sure a variable that is a date, needs to be sun to be set as one way, else any other day another way. 
Here is my code
BEGIN
SELECT CASE WHEN @IssueDate2(WEEKDAY, GETDATE()) = 1
THEN (set @IssueDate3_mjssun= CONVERT(VARCHAR(10),DATEADD(dd, -7, @IssueDate2),101))
ELSE (set @IssueDate3_mjssun= @IssueDate2) END --AS [Last Day]
END
SELECT @IssueDate3_mjssun
I'm open to any other ideas on how to do this.
Thanks!
Rudy

Answer 1

>> I'm open to any other ideas on how to do this. <<
We use CURRENT_TIMESTAMP and not the old Sybase/UNIX getdate() function call.
CASE is an expression; expression return values! You are using it as control flow, like you were writing BASIC or some other procedural language.
CONVERT() is another old Sybase string function. It was used by COBOL programmers who treat temporal data as strings and do display formatting in the program. SQL has temporal data types and we do display formatting in a presentation layer!
We need DDL. This is minimal Netiquette. If you want to be sure that a column is always a Sunday, then use a constraint: CREATE TABLE Foobar (issue_date DATE NOT NULL CHECK(issue_date DATEPART(WEEKDAY, issue_date) = 7, ..); This is another way that columns are not fields, that declarative SQL is not a procedural language.
If you use weeks as part of your business, I would build a calendar table with a ISO-8601 week-within-year format column in addition to the usual Common Era date. This format is 'yyyyWww-d' where yyyy is the year, W is a separator token, ww is (01-53) week number and d is (1-7) day of the week. You input any calendar date, find the week-within-year column and return the dates that match on a LIKE predicate. Ex: WHERE sale_day LIKE '2012W26-[67]'
In the ISO Standards, Sunday = 7. But Microsoft screwed up and had an incorrect default. They then added a kludge that allows you to set schema level parameters
>> I'm open to any other ideas on how to do this. <<
We use CURRENT_TIMESTAMP and not the old Sybase/UNIX getdate() function call.
CASE is an expression; expression return values! You are using it as control flow, like you were writing BASIC or some other procedural language.
CONVERT() is another old Sybase string function. It was used by COBOL programmers who treat temporal data as strings and do display formatting in the program. SQL has temporal data types and we do display formatting in a presentation layer!
We need DDL. This is minimal Netiquette. If you want to be sure that a column is always a Sunday, then use a constraint: CREATE TABLE Foobar (issue_date DATE NOT NULL CHECK(issue_date DATEPART(WEEKDAY, issue_date) = 7, ..); This is another way that columns are not fields, that declarative SQL is not a procedural language.
If you use weeks as part of your business, I would build a calendar table with a ISO-8601 week-within-year format column in addition to the usual Common Era date. This format is 'yyyyWww-d' where yyyy is the year, W is a separator token, ww is (01-53) week number and d is (1-7) day of the week. You input any calendar date, find the week-within-year column and return the dates that match on a LIKE predicate. Ex: WHERE sale_day LIKE '2012W26-[67]'
In the ISO Standards, Sunday = 7. But Microsoft screwed up and had an incorrect default. They then added a kludge that allows you to set schema level parameters
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