DBA Developer

Responsibilities  Designing Relational databases  Developing interface layer Environment Microsoft SQL Server,.NET SQL Layer: Stored procedures, functions,CLR Objects Object Layer: ADO. Net, Microsoft enterprise library, Object-Relational mappers  Query optimization/Performance tuning Code review for performance Missing indices

Applications  Single Sign on (SSO)  Search Solutions Search Database Search Engines  Import/Export solutions Sending to and receiving data from web services XML/CSV transformation  Frameworks  Data warehouse and OLAP

Challenges  Performance Missing index Poorly written queries Normalized vs. Denormalized Deadlocks  Design Schema flexible to changes DDL (data definition language) Vs DML(data manipulation language) ○ example

Simple example  Design a database to store user information Username,password, first name, last name, postal code Requirement changes , Address, City, Province, Country, language and etc now is needed to be stored. Solution ? CREATE TABLE Users ( UserID INT NOT NULL Primary Key, UserName NVARCHAR(50) NOT NULL, FirstName NVARCHAR(50) NULL, LastName NVARCHAR(50) NULL, PostalCode NVARCHAR(50) NULL );

Simple example  Option 1 add more column to the Users table  Option 2 insert rows instead of columns (How)

CREATE TABLE Users ( UserID INT NOT NULL Primary Key, UserName NVARCHAR(50) NOT NULL ); CREATE TABLE Properties ( PropertyID INT NOT NULL Primary Key, PropertyName NVARCHAR(50) NOT NULL ) CREATE TABLE UserProperty ( PropertyID INT NOT NULL Primary Key, UserID INT NOT NULL, value NVARCHAR(100) NOT NULL ) Many to Many Relation

XML DataType –Hybrid design CREATE TABLE Users ( UserID INT NOT NULL Primary Key, UserName NVARCHAR(50) NOT NULL, UserProperty XML ); CREATE TABLE Properties ( PropertyID INT NOT NULL Primary Key, PropertyName NVARCHAR(50) NOT NULL ) CREATE TABLE UserProperty ( PropertyID INT NOT NULL Primary Key, UserID INT NOT NULL, value NVARCHAR(100) NOT NULL )

XML DataType –Hybrid design  XML Advantages Flexibility Easy to parse and to serialized in to objects  Disadvantages Searching trough XML is Slow Maintenance – adds over head to insert and update  XML model is not a replacement for Relational model

Good to know about  Paging in SQL  Trees & Hierarchies in SQL  Graph in SQL  Recursive query in SQL (using Common Table Expressions)  XML manipulation (XPATH,XQUERY)  CLR objects in MS SQL Server