Datetime Types in SQL Server 2005:
Lets start with a quick look at the existing date time types in SQL Server. The datetime and smalldatetime, these two types are well known to us, So we wont be spending much time here.
|smalldatetime||YYYY-MM-DD hh:mm:ss||1 minute|
|datetime||YYYY-MM-DD hh:mm:ss[.nnn]||0.00333 second|
Though these types provide a whole lot of datetime functionality required for any database. The problem is that the date representation is always combined with the time in both the types and there is no way to represent the date only component or time only component in a database with out doing a lot of cast and convert.
New Datetime Types in SQL Server 2008
SQL Server 2008 has introduced four new datetime data types for the date and time representations in SQL Server Databases.
|datetime2[n]||YYYY-MM-DD hh:mm:ss[.nnnnnnn]||100 nanoseconds|
|datetimeoffset[n]||YYYY-MM-DD hh:mm:ss[.nnnnnnn] [+|-]hh:mm||100 nanoseconds|
The new Date type allows us to represents the date as an individual component with out the time field attached to it. And the Time type represents the Time as an individual component in databases. Note that the new Time type is at higher precision than the regular time in datetime type.
Datetime2 can be considered as an extension to regular datetime type with the time representation at an accuracy of 100 nanoseconds than at the regular 0.00333 seconds. The datetime2 type can be used with a default precision (datetime2(7)) or can be used with a user defined precision like datetime2(n) format.
If the time precision of datetime2 is set to 3 (datetime2(3)) which gives the exact equivalent representation of a regular datetime type.
DateTimeOffset is the combination of default datetime2 with the system time zone offset attached to it. The time zone offset displayed based on the Operating System date, time and culture settings. The offset should be between –14:00 to +14:00. The DateTimeOffset type does not support the day light saving times.
Here is my machine current datetimeoffset value 2010-04-25 23:24:07.7086518 +05:30. Notice that the time zone offset returned is +05:30 i.e. IST (Indian Standard Time) attached to datetime2 data.
New Date and Time Functions
|SYSDATETIME()||Similar to GETDATE() but it returns the current system date as new datetime2(7) type|
|SYSUTCDATETIME()||Similar to GETUTCDATE() but it returns the current system date in UTC as a new datetime2(7) type|
|SYSDATETIMEOFFSET()||Returns the current system date time as DateTime2(7) with system time zone offset attached to it|
|SWITCHOFFSET(expr, tz)||Function to convert the datetimeoffset in one time zone to a datetimeoffset in another timezone|
|TODATETIMEOFFSET(expr, tz)||Function to convert the datetime, datetime2 or datetimeoffset to a datetimeoffset with the specified time zone|
Conversions between different datetime types
1. How to convert datetime or datetime2 to datetimeoffset with specified time zone?
SELECT GETDATE(), TODATETIMEOFFSET(GETDATE(), '+08:30') -- results: 2010-04-26 00:18:36.927 | 2010-04-26 00:18:36.927 +08:30 SELECT SYSDATETIME(), TODATETIMEOFFSET(SYSDATETIME(), '+05:30') -- results: 2010-04-26 00:18:36.9316407 | 2010-04-26 00:18:36.9316407 +05:30
TODATETIMEOFFSET() combines the specified datetime or datetime2 to the specified time zone offset.
2. How to convert the datetimeoffset in one time zone to datetimeoffset in other time zone?
-- my current system time in IST (GMT + 5:30) SELECT SYSDATETIMEOFFSET() -- 2010-04-26 00:32:48.1838343 +05:30 -- IST (GMT + 5:30) converted to North America PST (GMT - 8:00) SELECT SWITCHOFFSET(SYSDATETIMEOFFSET(), '-08:00') -- 2010-04-25 11:02:48.1838343 -08:00 -- IST (GMT + 5:30) converted to Europe BST (GMT + 1:00) SELECT SWITCHOFFSET(SYSDATETIMEOFFSET(), '+01:00') -- 2010-04-25 20:02:48.1838343 +01:00
3. How to convert local datetime or datetime2 to UTC (Coordinated Universal Time)?
DECLARE @LocalDateTime datetime DECLARE @TimeZoneOffset INT -- convert my current system datetime to UTC SET @LocalDateTime = GETDATE() -- 2010-04-26 00:44:19.107 -- get the timezone offset of the system SET @TimeZoneOffset = DATEDIFF(MI, SYSDATETIME(),SYSUTCDATETIME()) -- 330 mins (i.e. 5:30 ) -- get the utc datetime SELECT DATEADD(MI,@TimeZoneOffset, @LocalDateTime) -- 2010-04-25 19:14:19.107
4. How to convert datetimeoffset to UTC?
DECLARE @DTO DATETIMEOFFSET -- convert my system datetimeoffset to UTC SET @DTO = SYSDATETIMEOFFSET() -- 2010-04-26 00:50:35.3701337 +05:30 -- switch offset to '+00:00' i.e. UTC SELECT SWITCHOFFSET(@DTO, '+00:00') ,CAST(SWITCHOFFSET(@DTO, '+00:00') AS DATETIME2) -- 2010-04-25 19:20:35.3701337 +00:00 | 2010-04-25 19:20:35.3701337
5. Other simple conversions?
SELECT CAST(GETDATE() AS Time) ,CAST(GETDATE() as date) ,CAST(SYSDATETIMEOFFSET() AS datetime2) -- results: 01:03:35.5700000 | 2010-04-26 | 2010-04-26 01:03:35.5971486 -- get timezone offset from datetimeoffset SELECT DATEPART(TZ, SYSDATETIMEOFFSET()) -- results: 330 (number of minutes)
The new date time types in SQL Server 2008 are more portable than datetime or smalldatetime and it is recommended to use them in the future development work.
Hope the post is helpful.
This problem seems trivial but there is no straight forward way to get this information. If you have tried the INSERT into EXEC command to insert the results of the sp_help_job procedure into a temporary table like below then you are familiar with the below error.
insert into #jobstatus
Msg 8164, Level 16, State 1, Procedure sp_get_composite_job_info, Line 72
An INSERT EXEC statement cannot be nested.
So you can not directly insert the results to a temp table from this procedure. Here is a trick I have used using the OPENROWSET to get around with the INSERT EXEC problem. This query results can be stored into a temporary table or a table variable using the INSERT INTO or SELECT INTO command which can be used for further processing.
select name, case when current_execution_status = 1 then ‘Executing’
when current_execution_status = 2 then ‘Waiting For Thread’
when current_execution_status = 3 then ‘Between Retries’
when current_execution_status = 4 then ‘Idle’
when current_execution_status = 5 then ‘Suspended’
when current_execution_status = 6 then ‘[Obsolete]’
when current_execution_status = 7 then ‘PerformingCompletionActions’
else NULL end as [status] from
openrowset(‘SQLNCLI’, ‘Server=(local);Trusted_Connection=yes;’,‘EXEC msdb..sp_help_job’)
Hope it helps
Just came to know about this book. More details on the Microsoft Press Blog.
The book contains 10 chapters and 216 pages, like so:
PART I Database Administration
CHAPTER 1 SQL Server 2008 R2 Editions and Enhancements 3
CHAPTER 2 Multi-Server Administration 21
CHAPTER 3 Data-Tier Applications 41
CHAPTER 4 High Availability and Virtualization Enhancements 63
CHAPTER 5 Consolidation and Monitoring 85
PART II Business Intelligence Development
CHAPTER 6 Scalable Data Warehousing 109
CHAPTER 7 Master Data Services 125
CHAPTER 8 Complex Event Processing with StreamInsight 145
CHAPTER 9 Reporting Services Enhancements 165
CHAPTER 10 Self-Service Analysis with PowerPivot 189
I have spent almost 3 hours to complete the script and test it for couple of sample scenarios during this weekend (31/01/10). The script initially drops all the objects of the schema and then drops the schema itself. It takes care of all the object dependencies with in the schema by dropping all of them in a specific order that will resolve the dependency issues.
The stored procedure takes two parameters SchemaName and the WorkTest. Use WorkTest equal to ‘t’ to print all the drop statements without executing them or specify anything else to execute the drop operations. The default option is ‘w’ i.e. Work for me.
EXEC CleanUpSchema 'MySchema', 't' -- debug GO EXEC CleanupSchema 'MySchema', 'w' -- work for me
These are the known limitations of the script
- It can not drop a PK table in the schema with an XML index or Spatial index defined
- It can not drop the schema which is referred by a XML schema collection
- Please let me know if you find any more issues with the script. I will list all of them here for others reference and will fix them to improve it further.
Hope it helps
The file group information of both an Index and a Table are stored in the sys.indexes table. You might wonder how the tables file group is stored in sys.indexes metadata table. It is because when ever a clustered index is created on a table in SQL Server the physical data pages of the table will be made part of the clustered index i.e. the leaf nodes of the clustered index contain the physical table data. So the clustered index file group is the file group of the table.
If there is no clustered index on the table then it is represented as a HEAP with index_id equal to ZERO in sys.indexes table.
At any point a clustered index with index_id equal to 1 or a heap with index_id equal to ZERO exists for a table in sys.indexes table. All non clustered indexes will have index_id greater than 1.
Below query gets the file group of the table Employee in HumanResources schema of AdventureWorks database.
SELECT d.name AS FileGroup FROM sys.filegroups d JOIN sys.indexes i ON i.data_space_id = d.data_space_id JOIN sys.tables t ON t.object_id = i.object_id WHERE i.index_id<2 -- could be heap or a clustered table AND t.name= 'Employee' AND t.schema_id = schema_id('HumanResources')
And below query gets the file group of the index ‘AK_Employee_rowguid’ on Employee table in HumanResources schema of AdventureWorks database.
SELECT d.name AS FileGroup FROM sys.filegroups d JOIN sys.indexes i ON i.data_space_id = d.data_space_id JOIN sys.tables t ON t.object_id = i.object_id WHERE i.name = 'AK_Employee_rowguid' AND t.name= 'Employee' AND t.schema_id = schema_id('HumanResources')
Please note that schema_id is important otherwise both the queries might return multiple results if you have same table name on different schemas.
Hope it helps
These are the two widely used SET options in SQL Server. Most developers explicitly set these options while creating Stored Procedures, Triggers and User Defined Functions but many are unclear on why we need to explicitly SET them? And why they are special compared to other options?
Below is the typical usage of these options.
SET QUOTED_IDENTIFIER ON GO SET ANSI_NULLS ON GO CREATE PROCEDURE SampleProcedure AS BEGIN -- select employees SELECT * FROM HumanResources.Employee END
Lets first understand what they exactly mean to SQL Server and then we will move on to why they are special.
SET QUOTED_IDENTIFIER ON/OFF:
It specifies how SQL Server treats the data that is defined in Single Quotes and Double Quotes.
When it is set to ON any character set that is defined in the double quotes “” is treated as a T-SQL Identifier (Table Name, Proc Name, Column Name….etc) and the T-SQL rules for naming identifiers will not be applicable to it. And any character set that is defined in the Single Quotes ‘’ is treated as a Literal.
SET QUOTED_IDENTIFIER ON CREATE TABLE "SELECT" ("TABLE" int) -- SUCCESS GO SET QUOTED_IDENTIFIER ON SELECT "sometext" AS Value -- FAIL because “sometext” is not a literal
Though the “SELECT” and “TABLE” are reserved keywords we are able to create the table because they are now treated as identifiers and the T SQL rules for identifier names are ignored.
When it is set to OFF any character set that is defined either in Single Quotes or in Double Quotes is treated as a literal.
SET QUOTED_IDENTIFIER OFF CREATE TABLE "SELECT"(“TABLE” int) -- FAIL GO SET QUOTED_IDENTIFIER OFF SELECT "sometext" AS Value -- SUCCESS as “sometext” is treated as a literal
SET ANSI_NULLS ON IF NULL = NULL PRINT 'same' ELSE PRINT 'different' --result: different SET ANSI_NULLS ON IF NULL IS NULL PRINT 'same' ELSE PRINT 'different' -- result: same
The default behaviour is ON in any database. As per BOL 2008 this option will always be set to ON in the future releases of SQL Server and any explicit SET to OFF will result an error. So avoid explicitly setting this option in future development work.
Why are these two options Special?:
These two SET options are special because whenever a stored procedure or a Trigger or a User Defined Function is created or modified with these options explicitly SET SQL Server remembers those settings. And every time the stored procedure is executed it always uses the stored settings irrespective of what the current user session settings are. So the behaviour of the stored procedure is not altered by the calling session settings and the usage of the SET option behaviour inside the SP is always guaranteed.
You can get any procedure or trigger or function settings for these options from the sys.sql_modules metadata table.
SELECT uses_ansi_nulls, uses_quoted_identifier FROM sys.sql_modules WHERE object_id = object_id('SampleProcedure')
And if you need to guarantee the behaviour for other SET options like SET ARITHABORT inside the SP then you need to SET them inside the procedure. The scope of the options specified inside the procedure is only applicable until the procedure completes its execution.
Hope it helps.
We have different providers to use (Microsoft OLE DB Provider for SQL Server or SQL Native Client) while creating SQL Server linked servers, or connecting to other sources like Excel, Access DB etc. This post gives brief overview of each of these providers and the difference between them.
ODBC is the programming API for connecting to any database management systems independent of vendor, operating system and programming languages. This was the first driver software designed for interacting with different Database Management Systems.
OLE DB is the Microsoft specific Data Access API for connecting to various Database Management Systems and extends the functionality of ODBC. This API was built using Microsoft COM technology and is part of the MDAC (Microsoft Data Access Components) which is installed with the Operating System or can be installed separately. MDAC includes the support for OLE DB, ODBC and ADO.
Till the SQL Server 2000 the SQL OLE DB and SQL ODBC connectivity was provided by MDAC package. But from SQL Server 2005 we have two different APIS
1. The Original MDAC which comes with OS
2. New API for SQL OLE DB, SQL ODBC and ADO which is called the SQL Native Client.
SQL Native Client combines the SQL OLE DB and SQL ODBC in MDAC into one DLL (SQLNCLI.DLL) which is shipped with the SQL Server and not part of the Operating System. So there is no dependency on the Operating System. As this DLL is shipped with the SQL Server every new release of the product might have a new version of SQL Native Client.
Now if you see the list of providers in SQL Server 2008 linked server creation wizard below; You can figure out that the providers listed with the prefix Microsoft are from the MDAC and SQL Native Client 10.0 is the SQL Server 2008 provider for SQL OLE DB and ODBC.
To create a linked server to SQL Server 2000 database we should use MDAC provider (Microsoft OLE DB Provider for SQL Server) and to SQL Server 2005 database we can use SQL Native Client provider or MDAC provider if you are not plannng to leverage the following new features offered by SQL Native Client.
- MARS (Multiple Active Result Sets in a single connection)
- XML Data Types
- CLR User Defined Types
- Asynchronous Data Access
- Database Mirroring
- Snapshot Isolation
Is there a Problem to existing Applications that use MDAC SQL OLE DB or ODBC connectivity on SQL Server 2005?
For the applications that use SQL ODBC and SQL OLE DB from MDAC there is no impact. But if you want to utilize the new features in SQL Server 2005 like UDTs or XML Types you need to use the SQL Native Client otherwise your applications should work fine.
For more information on the MDAC architecture you can go here.