WHAT’S NEW IN SQL SERVER 2008: T-SQL

Martin Bell

SQL Server MVP

Features we will look at:

• Date and Time Functionality• Dependency Reporting• Filestream Storage• Merge Statement• Row Constructors• Sparse Columns and Column Sets• Hierarchy ID Data Type• User Defined Table Type• Table Values Parameters

Date and Time Functionality

• Date• Supports Years 0 – 9999 i.e. 01-01-0001

to 31-12-9999 (Gregorian Calendar)• Native Datatype (not CLR)• Size - 3 bytes

Date and Time Functionality

• Time• Variable Precision - 0 to 7 decimal places

for seconds• Precise to 100 nanoseconds • Separate Date and Time saves space• Ansi compatible• Size - 3 bytes for precisions <= 2;

4 bytes for precisions of 3 and 4 5 bytes for precisions > 4

Date and Time Functionality

• DateTimeOffset• Supports Years 0 – 9999 i.e. 01-01-0001 to 31-12-

9999 (Gregorian Calendar)• Precise to 100 nanoseconds• Time Zone Offset (From UTCTime) Preserved• Not Time Zone Aware - No Daylight Saving Time

Support• Size - 8 bytes for precisions <= 2;

9 bytes for precisions of 3 and 4 10 bytes for precisions > 4

Date and Time Functionality

• DateTime2• Supports Years 0 – 9999 i.e. 01-01-0001 to 31-12-

9999 (Gregorian Calendar)• Precise to 100 nanoseconds• Size - 6 bytes for precisions <= 3;

7 bytes for precisions of 4 and 5 7 bytes for precisions > 5

Date and Time Functionality

• Can still use existing date/time functions• DATENAME (datepart, date)• DATEPART (datepart,date)• DATEDIFF (datepart, startdate, enddate)• DATEADD (datepart, number, date)• Datepart can also be microsecond, nanosecond,

TZoffset or ISO_WEEK• MONTH• DAY• YEAR• CONVERT extensions

Dependency Reporting

• New dependency views replace sp_depends

• Kept in sync as changes occur• sys.dm_sql_referenced_entities • Lists all named entities that an object references

• sys.dm_sql_referencing_entities• Lists all named entities that use an object

• Can see references at OBJECT, DATABASE DDL TRIGGER, SERVER DDL TRIGGER level

Filestream Storage

• Currently limited to 2GB with varchar(max)

• Poor streaming performance

• High cost of data

Filestream:

• Size limited by NTFS volume

• Kept transactionally consistent

• Can be stored on compressed volumes

Filestream Storage

• Check out Paul Randal’s Blog for the performance graphs

Filestream reads better than varbinary

Filestream inserts perform better for files over ≈2MB for Win32

Varbinary inserts perform than T-SQL Filestream

Filestream updates perform better for files over ≈1MB for Win32

Filestream updates perform better than varbinary for T-SQL

Filestream Storage

• SqlFileStream Managed API in VS 2008 SP1

Merge Statement

• Lets you INSERT, UPDATE, AND DELETE in a single operation (i.e. single pass of the data)

• Specify commands for each case (Insert, Update or Delete)

• Cannot be remote table of distributed partitioned view

• NOLOCK, READUNCOMMITED disallowed (to maintain index integrity)

• Special $ACTION column allows you to record whether MERGE did an INSERT, UPDATE, DELETE

Merge Statement

[ WITH <common_table_expression> [,...n] ]

MERGE

[ TOP ( expression ) [ PERCENT ] ]

[ INTO ] target_table [ [ AS ] table_alias ]

[ WITH ( <merge_hint> ) ]

USING <table_source>

ON <search_condition>

[ WHEN MATCHED [ AND <search_condition> ]

THEN <merge_matched> ]

[ WHEN [TARGET] NOT MATCHED [ AND <search_condition> ]

THEN <merge_not_matched> ]

[ WHEN SOURCE NOT MATCHED [ AND <search_condition> ]

THEN <merge_ matched> ]

<output_clause>

[ OPTION ( <query_hint> [ ,...n ] ) ]

;

Row Constructors (Values Clause)

Before SQL 2008:DECLARE @t TABLE (id int, name varchar(20));

INSERT INTO @t VALUESSELECT 1, 'Fred‘UNION ALL SELECT 2, 'Jim‘UNION ALL SELECT 3, 'Sue'

SQL 2008:DECLARE @t TABLE (id int, name varchar(20));

INSERT INTO @t (id, name) VALUES (1, 'Fred'), (2, 'Jim'), (3, 'Sue');

Row Constructors (Values Clause)

SQL 2008:DECLARE @t TABLE (id int, name varchar(20));

INSERT INTO @t (id, name )SELECT num, foreFROM (

VALUES (1, 'Fred'), (2, 'Jim'), (3, 'Sue')) d (num, fore);

Sparse Column and Column Sets

Ways of modeling sparse data:One row per attribute:

256 table limit in SQL Server JOIN

Multiple nullable columns one per attribute:

1024 column limit in SQL Server tables

Modeled as XML:Common properties are elements, sparse

are attributes

Hierarchy Id Data Type

• Compact way to store hierarchies with SELECT query support

• Can allow some hierarchy queries without having to resort to recursive queries

• Slower on re-parenting operations (not just moving pointers!)

• See BOL for discussions of the various trade-offs vs. XML and parent/child tables

Hierarchy Id Data Type

• CLRUDT implementation

• Uses ORDPATH representation (materialized path)

• "Level" property - allows breadth-first indexing

Hierarchy Id Data Type

• Depth First indexing

• Breadth First indexing

Hierarchy Id Data Type

• Methods for common hierarchical operations• GetRoot• GetLevel• IsDescendant• GetDescendant, GetAncestor• Reparent

User Defined Table Type

CREATE TYPE mytab AS TABLE (id int);DECLARE @t mytab;

Table Valued Parameters

How do I pass a table to a T-SQL stored procedure?

How do I efficiently pass multiple values from a database client?

Erland Sommarskog’s Web Sitehttp://www.sommarskog.se/arrays-in-sql.html

Table Valued Parameters

• Parameters must use strongly typed table variables

• Tables are passed by reference

• No Statistics support exposed on these, so be careful in large query plans

References (SQL 2008)

•What’s Newhttp://www.microsoft.com/sqlserver/2008/en/us/overview.aspx• Learning Resourceshttp://www.microsoft.com/sqlserver/2008/en/us/learning.aspx• Technet Insiders Bloghttp://blogs.technet.com/industry_insiders/• Technethttp://technet.microsoft.com/en-us/library/cc721270.aspx

References (Filestream)

• Should I store my images in the database (SQL 2000)

http://databases.aspfaq.com/database/should-i-store-images-in-the-database-or-the-filesystem.html• To BLOB or not to BLOBhttp://research.microsoft.com/research/pubs/view.aspx?msr_tr_id=MSR-TR-2006-45

References (Filestream)

• Paul Randal’s Bloghttp://www.sqlskills.com/blogs/paul/2008/03/09/SQLServer2008FILESTREAMPerformance.aspx• Guy Burstein's Bloghttp://blogs.microsoft.co.il/blogs/bursteg/archive/2008/05/12/sqlfilestream-managed-api-for-sql-server-2008-filestream.aspx

References (HierarchyId)

• Simon Sabin’s Bloghttp://sqlblogcasts.com/blogs/simons/• SQL Server Magazinehttp://www.sqlmag.com/articles/index.cfm?articleid=99369

References (Merge)

• Connor Cunningham’s Bloghttp://blogs.msdn.com/conor_cunningham_msft/archive/2009/02/04/conor-vs-merge-and-primary-key-collisions.aspx

Erland Sommarskog’s Articles http://www.sommarskog.se/arrays-in-sql.html http://www.sommarskog.se/arrays-in-sql-perftest.html

Guy Burstein’s blog http://blogs.microsoft.co.il/blogs/bursteg/archive/2007/12/02/sql-server-2008-

table-valued-parameters.aspx

Mike Taulty’s blog http://mtaulty.com/CommunityServer/blogs/mike_taultys_blog/archive/

2007/12/03/9991.aspx

References (TVPs)