1. T-SQL and XML Enhancements in SQL Server 2005 Eric Nelson Application Architect Microsoft http://blogs.msdn.com/ericnelhttp://blogs.msdn.com/ericnel (SQL Dev and UK ISV) http://blogs.msdn.com/ericnel

2. Many TSQL enhancements… Exception handling TOP(expression)PIVOT/UNPIVOTAPPLY Common Table Expressions Hierarchical queries RANK SNAPSHOT Isolation VARCHAR(MAX), VARBINARY(MAX)… XML Type Full Text Search improvements WAITFOR Event Notifcations on DDL and DML FOR XML TABLESAMPLE Service Broker BULK INSERT … Plus “none dev TSQL stuff” Online Index Rebuild SchemasCertificates Statement Level Recompile …

3. Exception Handling “If @@Error” programming sucks! There must be a better way…

4. Exception Handling: TRY/CATCH Eliminate tedious “if @@error” code Perform logging/cleanup when exceptions occur Ability to re-raise exceptions after cleanup BEGIN TRY END TRY BEGIN CATCH TRAN_ABORT END CATCH

5. Exception handling In CATCH block you can Use new built-in functions to retrieve error- number, message, severity Re-raise original exception or raise an alt Transaction abort Tx remains in “doomed” state until explicitly rolled back No actions which result in log writes may be performed in a doomed transaction – SELECT only until you ROLLBACK

6. TOP Drat …. I will not know until runtime how many rows I need…

7. TOP ( ) SQL 7.0 and 2000 Provided TOP (n) with constant expression Only for SELECT SQL Server 2005 Provides TOP ( ) Also available on INSERT/UPDATE/DELETE

8. TRY/CATCH TOP

9. PIVOT Columns, columns everywhere …. I need rows! (And Access can already do it!)

10. PIVOT PIVOT Transforms a set of rows to columns Similar to Access TRANSFORM Useful for data analysis Useful for open shemas E.g. Products with different properties UNPIVOT Reverse operation of PIVOT

11. PIVOTMakeYearSalesHonda19902000 Acura1990500 Honda19913000 Acura1991600 Make19901991Honda20003000 Acura500600 SELECT * FROM SalesTable PIVOT(SUM(Sales) FOR Year IN ([1990], [1991])) s

12. Common Table Expressions Temporary tables make some things so much easier to code– but that is so clunky… I need something better…

13. Common Table Expressions As per SQL-99 Syntax: WITH ( ) AS ( ) Both recursive and non-recursive forms Non-recursive: Tidy code, avoid temp tables, views, sub selects Recursive: Rewrite queries with derived tables to be more readable

14. Simple CTE --Average number of times a Product was ordered --for all Products that appeared on an order --more than 50 times WITH SalesCTE(ProductID, SalesOrderID) AS( SELECT ProductID, COUNT(SalesOrderID) FROM Sales.SalesOrderDetail GROUP BY ProductID ) SELECT AVG(SalesOrderID) FROM SalesCTE WHERE SalesOrderID > 50

15. Recursive CTEs Recursive, when references itself Recursive form of CTE UNION ALL Recursion stops when 2 nd SELECT produces empty results Initialize Accumulate

16. EXAMPLE: “Org Chart” No Recursive Queries DECLARE @RowsAdded int -- table variable to hold accumulated results DECLARE @reports TABLE (empid nchar(5) primary key, empname nvarchar(50) NOT NULL, mgrid nchar(5), title nvarchar(30), processed tinyint default 0) -- initialize @Reports with direct reports of the given employee INSERT @reports SELECT empid, empname, mgrid, title, 0 FROM employees WHERE empid = ‘12345’ SET @RowsAdded = @@rowcount -- While new employees were added in the previous iteration WHILE @RowsAdded > 0 BEGIN /*Mark all employee records whose direct reports are going to be found in this iteration with processed=1.*/ UPDATE @reports SET processed = 1 WHERE processed = 0 -- Insert employees who report to employees marked 1. INSERT @reports SELECT e.empid, e.empname, e.mgrid, e.title, 0 FROM employees e, @reports r WHERE e.mgrid=r.empid and e.mgrid <> e.empid and r.processed = 1 SET @RowsAdded = @@rowcount /*Mark all employee records whose direct reports have been found in this iteration.*/ /*Mark all employee records whose direct reports have been found in this iteration.*/ UPDATE @reports SET processed = 2 WHERE processed = 1 END

17. EXAMPLE: “Org Chart” With Recursive Queries WITH EmpCTE(empid, empname, mgrid) AS( SELECT empid, empname, mgrid SELECT empid, empname, mgrid FROM Employees FROM Employees WHERE empid = ‘12345’ WHERE empid = ‘12345’ UNION ALL UNION ALL SELECT E.empid, E.empname, E.mgrid SELECT E.empid, E.empname, E.mgrid FROM Employees AS E JOIN EmpCTE AS M FROM Employees AS E JOIN EmpCTE AS M ON E.mgrid = M.empid ON E.mgrid = M.empid) SELECT * FROM EmpCTE

18. DDL Triggers I need to control how people change the schema of my database…how?

19. DDL Triggers Extension of traditional triggers for DDL events Triggering events include all DDL statements CREATE_TABLE, ALTER_PROCEDURE, DROP_LOGIN, etc. Scoping at Database and Server levels Event data available inside trigger through eventdata() function

20. DDL Triggers -- Log tables being dropped to dropLog CREATE TABLE dropLog (id INT PRIMARY KEY IDENTITY, logTxt VARCHAR(MAX)) GO -- Trigger to log drops CREATE TRIGGER ddlDrop ON DATABASE AFTER DROP_TABLE AS INSERT INTO dropLog VALUES('A table has been dropped')

21. DML with Output It is a shame that I need to do two things to find out what rows I UPDATE or DELETE… is there a better way?

22. DML with OUTPUT OUTPUT clause for DML Ability to return rows as part of DML operations Use “Inserted” and “Deleted” columns available to get pre- and post-update values Option to store returned rows OUTPUT… INTO… DECLARE @MyTableVar TABLE (orderId int) -- Update all 'unprocessed' to 'processed’ UPDATE Orders SET status='processed' OUTPUT INSERTED.orderId INTO @MyTableVar WHERE status='unprocessed'

23. Ranking I want to rank my data based on criteria … no, I don’t just mean order it…

24. Ranking Functions: Scenarios Data analysis (RANK, DENSE_RANK, NTILE) Ability to generate ranks based on different criteria in same query Ability to separate presentation order from ranks Paging using ROW_NUMBER Common scenario for walking through result sets

25. DML with Output RANK SELECT RANK()OVER(ORDER BY City) as RANK, RANK()OVER(PARTITION BY City ORDER BY LastName) as PART_RANK, DENSE_RANK() OVER(ORDER BY City) as DENSE_RANK, ROW_NUMBER() OVER(ORDER BY City) as ROW_NUM, NTILE(4) OVER(ORDER BY City) as NTILE_4, LastName, FirstName, City FROM Employees ORDER BY City, LastName

26. SNAPSHOT Isolation Hmmm …… I need more work to happen in parallel. How? OR I am migrating from Oracle and want to do as few changes as possible

27. Snapshot Isolation SQL Server 2000 Transaction isolation levels Read Uncommitted Read Committed Repeatable Read Serializable SQL Server 2005 adds... Snapshot Two flavours: Statement = READ_COMMITTED Transaction = SERIALIZABLE

28. Snapshot Isolation Increased data availability for read applications Allows non-blocking consistent reads in an OLTP environment Writers don’t block readers Readers don’t block writers Permits writes, which can cause conflicts BUT…includes mandatory conflict detection Snapshot Isolation trades: cost of concurrency (locking exclusion) for cost of CPU & I/O to construct transaction consistent view and read over versions

29. Snapshot Isolation: Scenarios Reporting and ad-hoc queries running concurrently with OLTP Read-mostly database with relatively few writes Applications prone to deadlocks may behave better Consistent aggregates (e.g., AVG, SUM) Migration from versioning databases E.g. Oracle to SQL Server

30. Large data types I hate chunking data!!!! Please, tell me there is a better way…

31. …(max) Type Text/nText and Image have problems Most varchar functions don’t work (e.g. Like) Not directly updateable Not allowed as procedure variables Extension to varchar, nvarchar, varbinary up to 2GB CREATE TABLE myTable (Id int, Picture varbinary(max)) Picture varbinary(max))

32. XML I have rich XML outside the db – and strings inside the db . Is there a better way?

33. XML Support in SQL 2005 SQL Server 2005 as an XML store Durable, recoverable, consistent Mature management tools Integration with existing relational data SQL Server 2005 as an XML source Accessible over HTTP and SOAP Exposes all data as XML Can be programmed just like a web service

34. XML data type Native SQL type Use for column, variable or parameter CREATE TABLE docs (id INT PRIMARY KEY, xCol XML NOT NULL) CREATE TABLE docs (id INT PRIMARY KEY, xCol XML NOT NULL) Well-formed and validation checks Optional XML Schema enforcement Behaviours allow XQuery and extensions Exist, Query, Modify, Value Native XML Store XML Data Type

35. Native XML Store XML Index Create XML index on XML column CREATE PRIMARY XML INDEX idx_1 ON T (xCol) CREATE XML INDEX idx_2 ON T(xCol) CREATE XML INDEX idx_2 ON T(xCol) USING XML INDEX idx_1 FOR PATH USING XML INDEX idx_1 FOR PATH Creates indexes on structure (PATH), properties (PROPERTY) values (VALUE) Speeds up queries Entire query is optimised Same industry leading cost based optimiser Indexes are used as available

36. XML

37. Summary T-SQL is alive and kicking There is LOTS more than covered today Use T-SQL and CLR judiciously Links: Sample chapter http://www.yukonxml.com/chapters/aw/sql2005dev/ “A First Look at SQL Server 2005 for Developers” Addison Wesley: Bob Beauchemin, Niels Berglund, Dan Sullivan Books Online http://blogs.msdn.com/ericnelhttp://blogs.msdn.com/ericnel - click on “Download Books Online” on right http://blogs.msdn.com/ericnel

38. © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.