WHAT APPLICATION DEVELOPERS SHOULD KNOW ABOUT SQL SERVER?

Transcription

1 WHAT APPLICATION DEVELOPERS SHOULD KNOW ABOUT SQL SERVER? MILOŠ RADIVOJEVIĆ, PRINCIPAL DATABASE CONSULTANT, BWIN.PARTY, AUSTRIA SQL SATURDAY MUNICH, 8 TH OCTOBER 2016

2 Our Sponsors

3 Miloš Radivojević Data Platform MVP Principal Database Consultant, bwin.party Vienna, Austria Co-Founder: SQL Pass Austria MCT, MCITP, MCTS, MCP Conference Speaker: SQLBits, SQL Saturday Contact:

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5 Database Development Database Design Design, develop and implement database systems based on customer requirements Participate in database design and architecture to support application development projects Transact SQL Code Create complex functions, scripts, stored procedures and triggers to support application development Optimization Optimize database systems for performance efficiency Tables and Dictionaries Develop database tables and dictionaries Data Integrity Ensure data quality and integrity in databases Performance Identify any issues related to database performance and provide corrective measures Troubleshooting Troubleshoot database related issues in a timely fashion Testing Test databases and perform bug fixes Documentation Prepare design specifications and functional documentations for assigned database projects Improvements Evaluate existing database and recommend improvements for performance efficiency DBDEV Best Practice Develop best practices for database design and development activities

6 Who Should Create Database Objects And Write SQL Queries? Database Developers BUT, THERE IS A SMALL PROBLEM... THEY (ALMOST) DON T EXIST!

7 Software Development Life Cycle * chart taken from

8 Database Development in Real World Who is responsible for database servers? Database Administrators Who writes SQL code? Application Developers

9 Application Developer s Nice To Have s.net Framework 4 WPF WCF IIS C# Dependency Injection AngularJS Java TFS, SVN, GIT ASP.NET/ASP.NET MVC Xamarin XML Bootstrap Agile, Scrum Cassandra ADO.NET JQuery Node.js SOAP, REST Ajax Entity Framework Java Script HTML5, CSS3 Silverlight JSON SQL Server

10 Common Problems with SQL Code Performance Scalability Deployment

11 Common Performance Issues Bad Indexing Significant issues but usually easy and fast to fix by someone else ORM Tools Generate complex, suboptimized queries Developer does not need to know or learn Transact SQL You cannot be good developer without Transact SQL knowledge! Row-by-Row Processing Using Cursors Foreach loop - top hidden performance killer!

12 Using Cursors Cursors have a bad reputation And therefore are not used so frequently

13 Foreach Loop - Top Performance Killer

14 Foreach Loop - Top Performance Killer Return two most recent orders for each customer in the year 2005 if the amount is at least 1000

15 Foreach Iterative Approach Two queries (stored procs) and a loop

16 Foreach Iterative (Parallel) Approach Two queries (stored procs) and a loop, parellel processing

17 Foreach Batch Approach Single query (stored proc)

18 Foreach Loop - Top Performance Killer

19 Foreach Loop - Top Performance Killer Foreach approach is slow, why then devs use it? What they say? Business Logic belongs to Business Layer Why they do this really? They don t know how to achieve the same goal with a single query Iterative approach is slow and does not scale In addition they read significantly more data than needed Different excuses: Let s be flexible, We ll need them later...

20 Which SQL Server Features Are Important? Transact SQL FILESTREAM SQL Injection Backup/Restore AlwaysOn Indexing Create Tables Statistics Transactions SSIS Error Handling XML Support Spatial Data Partitioning SSAS Handling Deadlocks Cardinality Estimations Change Data Capture Execution Plans

21 Which SQL Server Features Are Important? Transact SQL FILESTREAM SQL Injection Backup/Restore AlwaysOn Indexing Create Tables Statistics Transactions SSIS Error Handling XML Support Spatial Data Partitioning SSAS Handling Deadlocks Cardinality Estimations Change Data Capture Execution Plans

22 What App Devs Need to Know? Transact SQL Window functions APPLY operator Avoid common developer mistakes T-SQL performance recommendations CREATE TABLE SQL Injection Transactions Other features and tools (SSIS, XML, DMVs)

23 Transact-SQL Knowledge CTE Window Functions APPLY Operator Paging Efficient find or remove duplicates Compare previous and current values (i.e. previous and actual order for specific customer) Find most recent N items for an outer record

24 Common Developer Mistakes Code issues Order of outer JOINS Placement of predicates and evaluation order NULL and NOT IN BETWEEN DISTINCT or TOP(1) as ad-hoc solutions for logical problems Deployment issues Creating index offline Unsafe and untested install files Missing EXECUTE permissions Delete/Update in Large Tables LOCK Escalation

25 SQL Injection

26 SQL Injection One of the most common methods of attack Who is responsible for it? Application Developer! How to prevent SQL Injection? Parametrization Stored Procedures Dynamic SQL => sp_executesql Prepared Statements Sanitizing input Least Privilege White List Monitoring

27 SQL Injection When you tell her that you didn t parameterize your queries P a r a m e t r i z e!

28 CREATE TABLE for App Developers Take time, discuss requirements Do not create a table in 2 mins! Do not create table with copy/paste BL implementation starts here! Changes are expensive nobody wants to pay for them

29 CREATE TABLE for App Developers Choose the right data type Do not use INT if you can reach the goal with SMALLINT Do not use DATETIME if you care about dates only (birthdate) Use database constraints If you know that possible values for a column are 1,2,3 create CHECK constraint. Otherwise someone will put 250 in the column and you will not know how to deal with it Try to minimize number of columns allowing NULL values Do not forget foreign keys or indexes Follow naming conventions

30 Transact-SQL Performance Tips Avoid functions in the WHERE clause Data type conversions Local variables Database constraints and performance Avoid scalar UDFs Be careful with NOLOCK Use readable secondary or database copy

31 Other Features And Tools DMV Identify slow stored procedures and queries Check execution frequency, table size, index usage... XML and JSON Export/Import XML/JSON data Native XML data type Cool use cases (using XML PATH to generate comma separated list of IDs) SSIS is still underused (export/import data)

32 Summary Transact-SQL The most important part of SQL Server surface for AppDevs Window Functions APPLY Operator Performance Tips and Recommendations You cannot be good developer without deep Transact SQL knowledge Other important things Avoid common mistakes Consider four aspects for each column during table creation SQL Injection Prevention Transactions Don t Underestimate Database!

33 Save the Dates! PASS Camp to 09. December 2016 SQL Konferenz to 16. February 2017

34 How did you like it? Please give feedback to the event: to me as a speaker: