MYSQL - How to get 1st, 2nd, 3rd etc... Monday, Tuesday, Wednesda, etc ... date in a month

Having trouble finding the 1st, 2nd, whatever day in a month.
I know the month and year. Say...  Sept. 2008
I want to know what is the Date of First Monday in that month. or Second Friday, etc.
I have seen some other functions in pSQL and Oracle but not MySQL. I have MySQL version 5.x
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Bob-VillaAsked:
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pssandhuConnect With a Mentor Commented:
Hey Bob-Villa:
Since I do not have access to MYSql database, below is a function that I created in SQL Server 2000 (TSQL) which does exactly what you asked for. However, there are couple of this things you need to know here:

1. The function below could cross over to next month if you pass high value to the @DayNum parameter.
2. Because it is coded in TSQL, you might have to change some syntax and function names to make it compatible to MySQL.

Here is an example on how to call this function in TSQL. Say for example you want to find out the first monday in September 2008:



FUNCTION CALL

Declare @Val Datetime
Select @Val =  pkamal.sp_GetWeekdayDate ('2008-09-01','MONDAY',1)
Print @val

Where @Date is always the first day of the Month in this September 01, 2008 ('2008-09-01'),
            @DayName is the name of the weekday you want to search which is this case in Monday, and
           @DayNum is the 1st, 2nd, 3rd etc @DayName('MOnday' in this case) if the select month.


FUNTION OUTOUT
This is th output by the function when the I ran it with same example as above:     Sep  1 2008 12:00AM



FUNCTION CODE:

CREATE FUNCTION sp_GetWeekdayDate (      @Date      Datetime,
                        @DayName       varchar(10),
                        @DayNum       Tinyint
                                                                 )
            RETURNS Datetime
AS

BEGIN

DECLARE @InitialDate      Datetime,
                @ReturnDate      Datetime

SET @InitialDate =CASE WHEN DATENAME(DW, @Date)= @DayName THEN @Date
                              WHEN DATENAME(DW, DATEADD(d,1,@Date))= @DayName THEN DATEADD(d,1,@Date)
          WHEN DATENAME(DW, DATEADD(d,2,@Date))= @DayName THEN DATEADD(d,2,@Date)
         WHEN DATENAME(DW, DATEADD(d,3,@Date))= @DayName THEN DATEADD(d,3,@Date)
         WHEN DATENAME(DW, DATEADD(d,4,@Date))= @DayName THEN DATEADD(d,4,@Date)
        WHEN DATENAME(DW, DATEADD(d,5,@Date))= @DayName THEN DATEADD(d,5,@Date)
                       WHEN DATENAME(DW, DATEADD(d,6,@Date))= @DayName THEN DATEADD(d,6,@Date)
         ELSE @Date
          END

SET      @ReturnDate = CASE WHEN @DayNum IS NULL or @DayNum In (0,1) Then @InitialDate
                           ELSE Dateadd(d,(7*(@DayNum-1)),@InitialDate)
                  END

RETURN (@ReturnDate)
END


Let me know if you still have issues understanding the logic or if you have issues converting over to MYSql.

Hope this helps.

P.
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dansotoCommented:
Do you want to find a particular record for the first day ?
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Bob-VillaAuthor Commented:
i want to know the date of the first monday in september of 2008 returned in MYSQL format. not the date of an actual record.
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_agx_Commented:
(No points please.  This is just a translation)

Here is a rough translation of pssandhu's function into MySQL. Watch out for line wrapping


delimiter //
 
CREATE FUNCTION fn_GetWeekdayDate (      
TheDate  Datetime,
DayName  varchar(10),
DayNum   Tinyint
)
RETURNS Datetime
BEGIN
  DECLARE InitialDate     Datetime;
  DECLARE ReturnDate      Datetime;
  DECLARE Dow int;
    
  SET InitialDate = 
	CASE WHEN Date_Format(TheDate, '%W') = DayName THEN TheDate
             WHEN Date_Format(Date_Add(TheDate, INTERVAL 1 DAY), '%W') = DayName THEN Date_Add(TheDate, INTERVAL 1 DAY)
             WHEN Date_Format(Date_Add(TheDate, INTERVAL 2 DAY), '%W') = DayName THEN Date_Add(TheDate, INTERVAL 2 DAY)
             WHEN Date_Format(Date_Add(TheDate, INTERVAL 3 DAY), '%W') = DayName THEN Date_Add(TheDate, INTERVAL 3 DAY)
             WHEN Date_Format(Date_Add(TheDate, INTERVAL 4 DAY), '%W') = DayName THEN Date_Add(TheDate, INTERVAL 4 DAY)
             WHEN Date_Format(Date_Add(TheDate, INTERVAL 5 DAY), '%W') = DayName THEN Date_Add(TheDate, INTERVAL 5 DAY)
             WHEN Date_Format(Date_Add(TheDate, INTERVAL 6 DAY), '%W') = DayName THEN Date_Add(TheDate, INTERVAL 6 DAY)
             ELSE TheDate
        END;
 
  SET ReturnDate = CASE WHEN DayNum IS NULL or DayNum IN (0,1) Then InitialDate
                        ELSE Date_Add(InitialDate, INTERVAL (7*(DayNum-1)) DAY)
                   END;
 
  /* uncomment this if you want to return null instead 
     of allowing crossover months
 
  SET ReturnDate = CASE WHEN Month(TheDate) = Month(ReturnDate) THEN ReturnDate 
   			ELSE NULL 
		   END;
  */
 
  RETURN ReturnDate;
END
//
 
delimiter ;
 
SELECT fn_GetWeekdayDate('2008-09-01', 'MONDAY', 1);

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_agx_Commented:
What was inadequate about pssandhu's suggestion? IMO it did exactly what the asker requested.  

I don't want any points for it, but did they try the translated version?  
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Bob-VillaAuthor Commented:
pssandhu provided sql code that did not work with mysql. agx provided a rough translation that needed some work. I was looking for some built-in function, or an advanced query that I was unfamiliar with, perhaps I didn't ask clearly. I was able to accomplish the same thing (in the 43 lines above) in 2 lines of perl code. If I were another user searching for the same solution I don't feel the answers given here would have been a great solution. Didn't mean to offend anyone, I was just trying to clean up my 2 open questions. Please don't respond with any additional comments I don't have time to debate this issue. I pay my $10 a month to find quick answers in a pinch, not to debate the quality of the answers given by other members.
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_agx_Commented:
No need for debate.  No further suggestions were offered because no other comments were made until now.  For future reference if a suggestion doesn't meet your needs, for whatever the reason, feel free to ask for alternatives :)  In addition, be sure to provide complete details about your environment so responders will know what options are available to you.



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