SQL Server - CLR integration

SQL Server 2008 for Developers
UTS Short Course

Peter Gfader
Specializes in
C# and .NET (Java not anymore)
TestingAutomated tests
Agile, ScrumCertified Scrum Trainer
Technology aficionado
Silverlight
ASP.NET
Windows Forms

Course Website
Course Timetable & Materials
http://www.ssw.com.au/ssw/Events/2010UTSSQL/
Resources
http://sharepoint.ssw.com.au/Training/UTSSQL/

Course Overview

What we did last weekHigh availability
?
What can go wrong? What can we do?
Implementing Database Snapshots
Configuring a Database Mirror
Partitioned Tables
SQL Agent Proxies
Performing Online Index Operations
Mirrored Backups

Homework?

SQL CLR Integration

Agenda - CLR Integration
What is .NET?
What is CLR Integration?
Requirements on SQL box
Samples
Internals
CLR Integration: Pros
CLR Integration: Cons
Real world - When to use CLR Integration

What is .NET?
An application development platform from Microsoft
Tools, Languages, Runtime (Virtual machine), IDE, …
Rapidly develop secure and robust software
Web and Windows
Full support for object-oriented programming

.NET Overview
IL = Intermediate Language
CLR = Runtime

CLR
Common
Language
Runtime
= Virtual machine

.NET Framework
Evolution
The whole .NET FX
http://shrinkster.com/1515(PDF Poster)

What is CLR Integration?
Lets you write your database queries using .NET
Create and debug using VS 2008 IDE
Brand new in SQL 2005 (Standard and Express)
Support for large UDT (User defined types) in SQL 2008 (up to 2GB)
Support for multiple inputs on UDA (User defined aggregators)
e.g. string concatenator that takes in a column and separator char
Any .NET language (C#, VB, C++)

SQL CLR Project

CLR Integration
You can do the same thing as SQL Server using .NET code
Stored Procedures
Triggers
User-defined functions
User-defined types
Aggregate functions

Server - Enabling CLR Integration
Enabled on an instance (not per database)
SQL Script
Execute sp_configure ‘clr enabled’, ‘1’
reconfigure

Stored Procedures

public partial class StoredProcedures
{
[Microsoft.SqlServer.Server.SqlProcedure]
public static void HelloWorld()
{
// Put your code here
using (SqlConnectioncn = new SqlConnection("Context Connection=true"))
{
cn.Open();
SqlCommandcmd = new SqlCommand("SELECT * FROM DEMO", cn);
SqlContext.Pipe.Send(cmd.ExecuteReader());
}
}
Sample

What you do
Enable CLR
Create a new database project in Visual Studio
Create a new stored procedure in Visual Studio
Connect to current context using “Context Connection=true”
Add a simple SELECT statement
Deploy and run it

Internals
Assembly collated as set of files
Stored within SQL Server system tables
Assembly, references, program database (pdb), source files
Deployed to SQL Server
Manually
Catalogued with CREATE ASSEMBLY
Dropped with DROP ASSEMBLY
Automatically
Deployed from VS 2008

Security Levels
Safe (default)
Access only to CLR code. No access is allowed to external resources, thread management, unsafe code or interop.
External_Access
Access is allowed to external systems, such as the EventLog, File System, and network. Still no access to unsafe code or interop code.
Unsafe
Access is not limited whatsoever. User-defined types

Custom CLR Functions

public partial class UserDefinedFunctions
{
[Microsoft.SqlServer.Server.SqlFunction]
public static boolIsValidPostCode(string postcode)
{
return System.Text.RegularExpressions.Regex.IsMatch(
postcode, ^(((2|8|9)d{2})|((02|08|09)d{2})|([1-9]d{3}))$");
}
};
Sample

What you do
Create IsValidPostCode in C# (.NET)
Deploy it to SQL Server
Run it

Stored procedure vs. Function
What is the difference?
Function
Base functionality
Independent of Database itself
Stored procedure
Many operations at once
Normally database specific

Triggers

public partial class Triggers
{
[Microsoft.SqlServer.Server.SqlTrigger(Name = "EmailTrigger", Target = "Customers", Event = "FOR UPDATE")]
public static void SalaryFraudTrigger()
{
SqlTriggerContext context = SqlContext.TriggerContext;
using (SqlConnectioncnn = new SqlConnection("context connection=true"))
{
cnn.Open();
SqlCommand command = cnn.CreateCommand();
command.CommandText = "SELECT * FROM inserted";
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
for (intcolumnNumber = 0; columnNumber<context.ColumnCount; columnNumber++)
{
SqlContext.Pipe.Send(string.Format("Col: {0} = {1}", columnNumber, reader[columnNumber].ToString()));
}
};
reader.Close();
}
}
}
Sample

What you do
Create EmailTrigger in C# (.NET)
Deploy it to SQL Server
Test it

CLR Integration: Pros (Continued)
Take advantage of the powerful .NET Framework
.NET is a full-featured programming language
Supports things like “for each” loops, arrays, collections
Object Oriented programming model to organise your queries
Obtaining data from external resources
The File System
The Event Log
A Web Service
The Registry

CLR Integration: Pros
For complex calculations
Parsing strings (like the regular expression code)
User-defined types
Date, time, currency, and extended numeric types
Geospatial applications
Encoded or encrypted data (see books online)
User-defined aggregates
Powerful Intellisense and debugging
Generally faster
E.g. CLR aggregate 100x faster than cursor

CLR Integration: Cons (Continued)
NON MAINSTREAM
Lots of programming for simple operations
Some overhead in communicating with assemblies
Remember – T-SQL is designed and optimised for data, use it!
Not useful if your guys do not know any .NET
Potentially costly to rewrite logic
Companies (including us) have invested a lot in T-SQL

CLR Integration: Cons
There are some restrictions to observe when calling between T-SQL and SQL-CLR.
You must only use T-SQL supported data types (No streams)
You can't use inheritance or polymorphism
.NET cannot easily represent either VARCHAR or TIMESTAMP
.NET strings are Unicode, the equivalent of NVARCHAR
The CLR decimal type is not the same as SQL_DECIMAL

When to use CLR Integration
Do I need to manipulate data before it is displayed?
.NET code and SQLCLR
Do I need to do set-based operations such as pivoting?
T-SQL
Do I need to do extensive computation or custom algorithms?
Are my developers SQL gurus but .NET newbies?
T-SQL
Do I have loads of stored procs that are becoming hard to manage?

CLR Integration
The Bottom Line
Use T-SQL for all data operations
Use CLR assemblies for any complex calculations and transformations

Quick tips
SQL Management Studio Shortcuts
Ctrl + L – Display query execution plan
F5 – Run/Show result grid
Rules for SQL Server
http://www.ssw.com.au/SSW/Standards/default.aspx
SQL Server Cheat sheet
http://www.pinaldave.com/sql-download/SQLServerCheatSheet.pdf
http://www.addedbytes.com/cheat-sheets/sql-server-cheat-sheet/

Session 4 Lab
CLR Integration
Download from Course Materials Site (to copy/paste scripts) or type manually:
http://tinyurl.com/utssql2009

3things…
PeterGfader@ssw.com.au
http://peitor.blogspot.com
twitter.com/peitor

2 Things
PeterGfader@ssw.com.au
EricPhan@ssw.com.au

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SQL Server - CLR integration

by Peter Gfader

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