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 BRATISLAVA, 4 TH JUNE 2016

2 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, SQLKonferenz SQL Pass Austria, SQL Nexus, SQLU Summit, TUGA IT Contact:

4 Bwin GVC

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 Haves WPF WCF C# Dependency Injection IIS AngularJS.NET Framework 4 Java TFS, SVN, GIT Bootstrap ASP.NET/ASP.NET MVC Xamarin Agile, Scrum XML SOAP, REST JQuery Node.js Ajax Entity Framework ADO.NET Average application developer is not up-to-date with SQL Server features and his/her knowlege ends up with GROUP BY clause Java Script HTML5, CSS3 Silverlight JSON SQL Server Cassandra

10 Common Problems with SQL Code Common Problems with the code written by Application Developers Performance Scalability Deployment

11 Performance Issues Caused By Bad Indexing Significant issues but usually easy and fast to fix by someone else Object-Relational Mapping (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 - not frequently used due to bad reputation Hidden Top Performance Killer foreach loop

12 Using Cursors

13 Foreach Loop - Top Performance Killer

14 Foreach Loop - Top Performance Killer

15 Foreach Iterative Approach

16 Foreach Parallel Approach

17 Foreach Batch Approach

18 Foreach Loop - Top Performance Killer Why developers use iterative approach with for each loop to retrieve or manipulate data in a database? 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...

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

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

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

22 Window Functions 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

23 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

24 SQL Injection

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 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 Recommendations Functions in the WHERE clause Data type conversions Local variables Database constraints and performance Avoid scalar UDFs Be careful with NOLOCK If you are not an expert => follow recommendations! 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 Export/Import XML 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 The most important part of SQL Server surface for AppDevs is Transact SQL 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