Calendar Table in SQL Server

What is Calendar Table in SQL Server ?

Calendar Table is a custom/user table in SQL Server created for ease of users coding. At times, it is observed many programmers are struggling to write date/calendar queries. Also, it is observed online processing of these functionalities has its own performance impact. As mentioned, Calendar table would come in time to save programmers as those are pre populated and quite easy to use as well.

Calendar Table Code

Drop Table if exists Calendar;

Create Table Calendar 
	Date Date Primary Key, DayNo TinyInt, MonthNo TinyInt, YearNo SmallInt
	, WeekNo TinyInt, ISOWeekNo TinyInt,WeekDayNo TinyInt
	, DayName Varchar(10), MonthName Varchar(10), QuaterNo TinyInt
	, DayOfYearNo SmallInt, IsWeekEnd TinyInt
	, IsHoliday TinyInt, HolidayDescription nVarchar(500)

;with cteSeed  as ( Select 0 Seed union all Select Seed +1 From cteSeed where Seed <=100000)
,     cteDateDimenion as ( Select dateadd(Day,Seed,cast('1990-01-01' as date) ) Date from cteSeed)
,     cteCalendar as (
		         Date,Day(Date)DayNo,Month(Date) MonthNo, Year(Date) YearNo 
			,DAtePArt(Week,Date) WeeKNo, DATEPART(ISO_WEEK,Date) ISOWeekNo,DATEPART(WEEKDAY,Date) WeekDayNo
			,DAteName(WEEKDAY,Date) DayName, DAteName(Month,Date) MonthName
			,DATEPART(Quarter,date) QuaterNo, DATEPART(DAYOFYEAR, date) DayOfYearNo
			,Case when DAteName(WEEKDAY,Date) in ('Saturday','Sunday') Then 1 Else 0 End 'IsWeekEnd'
			,Case When Day(Date)=1 and Month(Date)=1 Then '|New Year Day|' 
					When Day(Date)=25 and Month(Date)=12 Then '|Christmas Day|' 
					Else '' End  
			+ Case when DAteName(WEEKDAY,Date) in ('Saturday','Sunday') Then '|' 
			+  DAteName(WEEKDAY,Date) + '|' Else '' End as HoliDayDescription
		From cteDateDimenion )
Insert into Calendar (Date,DayNo,MonthNo,YearNo,WeekNo,ISOWeekNo,WeekDAyNo
Select Date,DayNo,MonthNo,YearNo,WeekNo,ISOWeekNo,WeekDAyNo
,DayName,MonthName,QuaterNo,DayOfYearNo,IsWeekEnd,NULL,HolidayDescription From cteCalendar

Update Calendar Set IsHoliday = Case when Len(HoliDayDescription) > 0 Then 1 Else 0 End 

Select * From Calendar


1. The week day starts from Sunday.

2. Holiday list is specific to country, so the code above is as an example, feel free to add your specific holidays.

Use Cases:

How do you calculate business/working days between two dates?

Select count(1) as 'No. of Business Days' From Calendar 
where Date between '2020-01-01' and '2020-12-31' and IsHoliday != 1

How do I get Day name of first day of given month and year?

Select Date,DayName FRom Calendar where YearNo=2020 and MonthNo =11 and DayNo=1

I am sure, there many other use cases it would be helpful in real time, keep explore and feel free to make modification as required.

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When was the database taken offline/online in SQL Server

Here is a script to identify when was the database taken offline/online and few other information like login name, host name and application name.


DECLARE  @DBNAME nvarchar(100)
  ,@FileName nvarchar(max)
  ,@Status nvarchar(10)
SET @Status = 'OFFLINE' --Provide [OFFLINE / ONLINE]
SELECT @FileName=[path] FROM sys.traces WHERE is_default=1

DECLARE @ErrorLogTable table (Logdate datetime, ProcessInfo nvarchar(10), [Text] nvarchar(max))

INSERT INTO @ErrorLogTable
EXEC xp_readerrorlog 0,1, @Status, @DBNAME, NULL, NULL, 'desc'

SELECT Distinct DatabaseID, DatabaseName, HostName, ApplicationName, LoginName, StartTime, B.ProcessInfo, B.Text
FROM sys.fn_trace_gettable( @FileName, DEFAULT ) A
Inner join @ErrorLogTable B on A.SPID = cast(SUBSTRING(B.ProcessInfo,5,5) AS int)
and CAST(StartTime AS nvarchar)=cast(B.Logdate AS nvarchar) 

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How do we list the available instances from SQL Server

Here is a script to list the available instances of a SQL Server.


DECLARE @regpath NVARCHAR(128)

DROP TABLE IF EXISTS #AllInstancesOnMachine, #CurVer
CREATE TABLE #AllInstancesOnMachine (InstanceName VARCHAR(128), RegPathToUse VARCHAR(128), MajorVersionFound VARCHAR(50))
CREATE TABLE #CurVer (RegValue VARCHAR(128), VersionFound VARCHAR(50))

INSERT INTO #AllInstancesOnMachine (InstanceName, RegPathToUse)
EXEC   master..xp_instance_regenumvalues
	@rootkey = N'HKEY_LOCAL_MACHINE',
	@key     = N'SOFTWARE\\Microsoft\\Microsoft SQL Server\\Instance Names\\SQL'

SELECT InstanceName, RegPathToUse FROM #AllInstancesOnMachine

OPEN VersionCursor

WHILE (1=1)
	FETCH NEXT FROM VersionCursor INTO @Inst, @regpath

	SET @regkey = N'Software\Microsoft\Microsoft SQL Server\'


	INSERT INTO #CurVer (RegValue, VersionFound)
	EXECUTE master.sys.xp_regread
		@rootkey		= N'HKEY_LOCAL_MACHINE',
		@key			= @regkey,
		@value_name		= N'CurrentVersion'
	UPDATE #AllInstancesOnMachine SET MajorVersionFound = 
			(SELECT CASE Parsename(VersionFound,4)  when 10 then 'SQL 2008 or 2008 R2'
								when 11 then 'SQL 2012'
								when 12 then 'SQL 2014'
								when 13 then 'SQL 2016'
								when 14 then 'SQL 2017' End FROM #CurVer) 
	WHERE InstanceName = @Inst


CLOSE VersionCursor
DEALLOCATE VersionCursor

SELECT * FROM #AllInstancesOnMachine

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A way to Shrink Data File in SQL Server

Problem Statement

We recently wanted to drop few obsolete tables those are really big ones in my SQL Server databases. Post clean up, meaning dropping the tables, we would like to reclaim the space it occupied to OS and reduce the cost associated with. What are the best options in such situations?

DBA’s Ponderings

Usually, DBAs would never support shrinking of data file due to several reason. They consider about their system performance than the disk cost, especially, now days, the worry on cost associated must be an outdated belief. Shrink can cause many bad on your databases and some of them are listed as below:

1. It increases the fragmentation.

2. It will have a system performance issues due to heavy fragmentation.

3. While running shrink a data file, it may have dangerous locking issues. This must be an offline activity.

4. If shrink file on a LOB data, that would slow down the process badly.

Due to all the above reasons, we should always keep a long distance to shrink file operations. Thats not our best friend for our system.

Then, How do we shrink data file?

Then, What we do if its mandatory to do shrink the data file as our initial Problem Statement?

If its mandatory or meaningful or sensible, then you can do with few extreme considerations. In one of my case, I had to clean up almost 1000 tables from a database and I had to do this for almost 2000 databases. It had almost 4GB data to be cleared from a single database resulting a whooping amount of cost save! This is a real example where shrink file is important or a valid reason to do so. Myself & one of my colleague “Pascal Benguigui” have come up with an approach here as below.

Let us look at the options/considerations to apply shrink file as below. It may vary for others, but its more of our deliberate thoughts.

1. Understand the size of data that you wanted to eliminate. To understand, I would suggest you to take backup and restore your database to local and remove the data followed by shrink file and then identify the current size of data file.

2. If the file size if more than 1000 MB, we can consider shrinkfile, otherwise, it may not be so efficient.

3. If the file size is more than 1000 MB, let us also consider the percentage of free space. If free space percentage is lesser than 10%, it may not be so efficient again.

4. Let us also shrink the file up to the used space and 10 percentage added to the space. This must be a good number, but depends!, it may or may not suitable for all cases. A detailed analysis can be carried out and define as per your environment leaving it to the respective DBA’s descretion.

Shrink Script

CREATE OR ALTER procedure Shrink_DataFile @db varchar(200)

declare @f_name varchar(200)
declare @f_file varchar(500)
declare @f_size int
declare @f_used int
declare @pct_free int
declare @f_newsize int
declare @sql_query nvarchar(2000)
declare @sql_param nvarchar(200)

print 'Datafile SHRINK requested on database ['+@db+'] : '
declare cur_name cursor for 
select name from sys.sysaltfiles where dbid=db_id(@db) and groupid=1 and CONVERT(sysname,DatabasePropertyEx(@db,'Updateability'))='READ_WRITE' order by fileid asc

open cur_name
fetch next from cur_name into @f_name

while @@fetch_status=0

       select @sql_param =N'@f_size_out int OUTPUT,@f_used_out int OUTPUT,@f_file_out varchar(500) OUTPUT'
       select @sql_query=N'use ['+@db+']; select @f_size_out=CAST(s.size/128.0 AS int) , @f_used_out=CAST(FILEPROPERTY(, ''SpaceUsed'')/128.0 AS int),@f_file_out=filename from sys.sysfiles s where groupid=1 and name='''+@f_name+''''
       EXEC sp_executesql @sql_query, @sql_param, @f_size_out=@f_size OUTPUT, @f_used_out=@f_used OUTPUT,@f_file_out=@f_file OUTPUT ;
       select @pct_free=(@f_size-@f_used)*100/@f_size

       if @f_size >1000 and @pct_free>10
             -- shrink should keep 10% free space and be a multiple of 100 higher
             select @f_newsize=@f_used*1.1
             select @f_newsize=ceiling(cast(@f_newsize as decimal(38,2))/100)*100
             if @f_newsize < @f_size
                    print 'File "'+@f_file+' (size '+convert(varchar,@f_size)+' MB) " will be shrinked to '+convert(varchar,@f_newsize)+' MB ...'
                    select @sql_query=N'USE ['+@db+']; 
                    DBCC SHRINKFILE (N'''+@f_name+''' , '+convert(varchar,@f_newsize)+')  WITH NO_INFOMSGS'
                    print @sql_query
                    exec sp_executesql @sql_query

                    select @sql_param =N'@f_size_out int OUTPUT'
                    select @sql_query=N'use ['+@db+']; select @f_size_out=CAST(s.size/128.0 AS int) from sys.sysfiles s where groupid=1 and name='''+@f_name+''''
                    EXEC sp_executesql @sql_query, @sql_param, @f_size_out=@f_size OUTPUT;
                    print '... New size for file "'+@f_file+'" shrinked is '+convert(varchar,@f_size)+' MB
                    print 'NO SHRINK : New size estimated for file "'+@f_file+'" ('+convert(varchar,@f_newsize)+' MB) not lower than the current file size ('+convert(varchar,@f_size)+' MB)'

             print 'NO SHRINK : Size requirements not valid to shrink file "'+@f_file+' (size '+convert(varchar,@f_size)+' MB / free space '+convert(varchar,@pct_free)+' %)

       fetch next from cur_name into @f_name
       close cur_name
deallocate cur_name

if @f_file is null
       print 'database ['+@db+'] not existing or not in READ-WRITE mode


Post shrinkfile, we would expect lots of fragmentations. This can severely impact the system performance. We need to make sure that we need to avoid fragmentation as quickly as possible by running INDEX rebuild/reorganize. There is a well defined index maintenance solution defined by Ola Hallengren that can be used for the same.

If you have to plan it for many number of databases, you need to consider this to happen in multiple batches to ensure that this process does not hurt the system. There may be a chance that your immediate backup jobs taking longer time than usual. Importantly, we need to make sure the shrink followed by index defragmentation is planned at application off peak hours, otherwise it might end up with larger number of blocking/locking scenarios.

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How to get FQDN (fully qualified domain name) from SQL Server?

A fully qualified domain name (FQDN) is referred to as an absolute domain name, is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS).

You can see this information easily throughput Control Panel – > System and Security – > System – > Look out “Computer name, domain and workgroup settings”

But, I was looking for some way to identify this information without switching my windows (actually I was working on something when I was asked this information) .

EXEC master..xp_loginconfig 'Default Domain'

DECLARE @rootkey varchar(100) = 'HKEY_LOCAL_MACHINE',
@key varchar(100) = 'SYSTEM\ControlSet001\Services\Tcpip\Parameters\',
@value_name varchar(100) = 'Domain',@Domain_Name sysname -- output parameters
--Using xp_regread
EXEC master..xp_regread @rootkey = @rootkey, @key = @key, @value_name=@value_name
--Using xp_instance_regread
EXECUTE master.sys.xp_instance_regread
    @rootkey = @rootkey, @key = @key, @value_name=@value_name

/* Incase you need to assign to a variable*/
EXEC master..xp_regread @rootkey = @rootkey, @key = @key, @value_name=@value_name,@value=@Domain_Name OUTPUT 
SELECT @Domain_Name 'Domain Name'

Set @Domain_Name = ''

EXECUTE master.sys.xp_instance_regread
    @rootkey = @rootkey, @key = @key, @value_name=@value_name,@value=@Domain_Name OUTPUT 

SELECT @Domain_Name 'Domain Name'
Since, its domain information, I am not providing the screenshot, you may try it out yourself and share your thoughts.

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