So, this is not a big tip, but worth at least 10 minutes to figure it out on your own.  Here is to saving you 10 minutes:

SELECT LEFT (userlastname, 1) as alpha,       count(id)FROM attendeesWHERE id IN (              SELECT attendeesid              FROM AttendeesCodeCampYear              WHERE codecampyearid = 6      )GROUP BY  LEFT (userlastname, 1)OORDER BY LEFT (userlastname, 1)

It’s pretty self explanatory.  Our case is we have two tables that we track code camp attendees.  One is the master list, and the other is a detail by year.  (6 is this year)

And, the results:

> NULL    1

>        6

> .       1

> @       1

> _       18

> A       319

> B       488

> C       543

> Ç       2

> D       313

> E       84

> F       169

> g       368

> H       340

> I       49

> J       190

> K       474

> L       460

> M       592

> N       255

> O       79

> P       427

> Q       14

> R       336

> S       776

> T       302

> u       27

> V       191

> w       296

> X       21

> y       176

> Z       100

Say you want to delete all but the last 30 days of activity.  If you just simply say DELETE FROM table WHERE id>10000, you will cause this to happen in one transaction and likely, you will get an error.  That’s the best case.  The worst case is your system tries to do this, eventually consumes all the resources in your computer and crashes your server.

CREATE PROCEDURE dbo.DeleteRowsInGroupsBeforeNdaysLog4NetAll@NoOfRowsToDelete int,@DaysBeforeTodayToDelete intASBEGIN

  DECLARE @DateToDeleteBefore date    -- Number Of Days To Delete Records From  DECLARE @DateToday datetime         -- To Hold Todays Date  DECLARE @PrintMessage varchar(256)  -- To Hold Print Message          DECLARE @CurrentRowCount int        -- Scratch Var For Counting Rows

  SET @DateToday = GetDate()

  SELECT @CurrentRowCount =         (           SELECT COUNT(*)           FROM dbo.Log4NetAll           WHERE Date <(@DateToday - @DaysBeforeTodayToDelete)         ) 

  WHILE (@CurrentRowCount > 0) BEGIN      DELETE TOP (@NoOfRowsToDelete)      FROM dbo.Log4NetAll        WHERE Id IN (        SELECT TOP (@NoOfRowsToDelete) Id         FROM Log4NetAll        WHERE Date < (@DateToday - @DaysBeforeTodayToDelete)        ORDER BY Id ASC)

       -- Count the records again       SELECT @CurrentRowCount =         (           SELECT COUNT(*)           FROM dbo.Log4NetAll           WHERE Date <(@DateToday - @DaysBeforeTodayToDelete)         )        SET @PrintMessage = N'Deleting This Many Rows: '                            + (CAST(@CurrentRowCount AS nvarchar(10)));       PRINT @PrintMessage;  END  END

Then, do Execute the Procedure, you would call it as follows assuming you wanted to delete the code in batches.

DECLARE @NoOfRowsToDelete int;DECLARE @DaysBeforeTodayToDelete int;

SET @NoOfRowsToDelete = 100;SET @DaysBeforeTodayToDelete = 30;

EXEC [dbo].[DeleteRowsInGroupsBeforeNdaysLog4NetAll]   @NoOfRowsToDelete, @DaysBeforeTodayToDelete ;

The output of calling this might be:

Query execution was canceled by user request.

Deleting This Many Rows: 19199

Deleting This Many Rows: 19099

Deleting This Many Rows: 18999

Deleting This Many Rows: 18899

Deleting This Many Rows: 18799

Deleting This Many Rows: 18699

Deleting This Many Rows: 18599… (All the way until 0)

Hope this helps!

So, first thing I do is fire up Microsoft SQL Server Management Studio, create a new query (it does not matter what database because I’m going to simply execute some TSQL.

Basically, I’m going to write some simple TSQL to create a variable with today’s date (and time) in it, then use the function DATEADD and create a new date with 1 hour less.  Here is the code:

DECLARE @MyDate datetimeDECLARE @NewDate datetime

SET @MyDate = GetDate();SET @NewDate = DATEADD(HOUR,-1,@MyDate);

PRINT @MyDatePRINT @NewDate

And, after pasting it in Microsoft SQL Server Management Studio, you can see the output when pressing execute.

Now, we’ve proven to ourselves we no how to subtract an hour, let’s apply it to a simple SQL Statement and presto, problem solved.  Here is the final simple SQL that does the job.

UPDATE Load SET ProcessedDate=DATEADD(HOUR,-1,ProcessedDate) WHERE Id=954249

It occurred to me I could do it in LINQ, then grab out the SQL it generated.  The tool?  LINQPad of course.  So, here is what I typed into LINQPad:

(from data in Attendees
let dateNoTime =
    new DateTime
     (data.CreationDate.Value.Year,
      data.CreationDate.Value.Month,
      data.CreationDate.Value.Day)
orderby dateNoTime
group data by dateNoTime into g
where g.Count() > 0
select new
    {
    g.Key,
    Number_Registered = g.Count()
    }).OrderByDescending(f=>f.Key)

Then, After pasting that into LINQPad, choosing the SQL tab on the bottom, it gives me this:

SELECT [t2].[value3] AS [Key], [t2].[value2] AS [Number_Registered]
FROM (
SELECT COUNT(*) AS [value], COUNT(*) AS [value2], [t1].[value]
          AS [value3]
FROM (
    SELECT CONVERT
         (DATETIME, CONVERT(NCHAR(2), DATEPART(Month, [t0].[CreationDate]))
           + ('/' + (CONVERT(NCHAR(2), DATEPART(Day, [t0].[CreationDate])) +
              ('/' + CONVERT(NCHAR(4), DATEPART(Year, [t0].[CreationDate]))))), 101)
                    AS [value]
        FROM [Attendees] AS [t0]
        ) AS [t1]
    GROUP BY [t1].[value]
    ) AS [t2]
WHERE [t2].[value] > @p0
ORDER BY [t2].[value3] DESC

And, the nice screen shot of LINQPad

And, it works perfect!  Even the TSql generated looks pretty nice.  Group By, Convert, DatePart and everything. Somehow, I feel like I’ve cheated, but I’m good with that in this case.

Hope this helps!