COP2360 – C# Programming Chapter 14 – Nov 25, 2015

Announcements Three Weeks Left – Next Week ASP.NET (Web) Development Part II of Assignment 5 – December 9 Part III of Assignment 5 Final Exam Review Final Exam Programming Assignment – December 16 Final Exam Please Sign on to Panther Web and complete the Student Assessment for this course!! I might bring better candy to the final if you all do!!

Tonight Database Access Assignment 5 – Part I

Flat File Access to Data Fields are “hard” to define and have to be converted to variables once the data is read Relationships between data difficult to define – For example, our Assignment 4 had Questions and Answers with the Answers being related to specific questions. The best we could do was to have the Answer follow the Questions. – We needed to show which answer was correct, so we used an asterisk. Multiple access to the same information almost impossible – Once a File is opened by a program, it is locked from being opened by other programs. Every file needed it’s own set of definitions to be understandable by the program.

What is a Database A large, integrated collection of data. – Models a real-world enterprise. – Entities a Noun (e.g., students, courses) Attributes – The fields within the Entity – Relationships a Verb that relates two or more Nouns Usually answers a question (e.g., Which courses is Madonna taking this summer?)

What is a Database Management System (DBMS) A software package designed to store and manage databases

Why Use a DBMS? Data independence and efficient access. Reduced application development time. Data integrity and security. Uniform data administration. Concurrent access Data Security/Recoverability

Relational Data Model Main concept: relation, basically a table with rows (sometimes called tuples) and columns. Every relation has a schema, which describes the columns or fields (or attributes) within the table. Both entities and relationships can be described in a relation.

Major Relational Players Oracle – Large scale corporation databases financials inventory Microsoft SQL Server – Small to medium corporation databases – Integrated tightly with other Microsoft products – Similar product support as Oracle MySQL (now owned by Oracle) – #1 Open Source database – used by many social media sites (Facebook, Twitter, etc.)

Data Definition Language (DDL) Used to define the schema and manage the database structure – Create Table – Alter Table – Create Index

Data Manipulation Language (DML) Commands to add, update and delete records in the database – INSERT – UPDATE – DELETE Commands to query the database – SELECT

NoSQL Databases To try and provide for access to massively large data sets, several companies have developed what are named “NoSQL” (for Not Only SQL) databases – Several different models using different data structures. – Basics include the splitting of data into a self defining database across multiple servers. XML of JSON (or other) self defining methods employed As data grows, more small servers can be added instead of having to increase capacity of one server When multiple servers are used, “ACID” is going to severely slow down the update and retrieval processes. – Each version has it’s own unique data definition and data manipulation languages.

Microsoft Visual Studio Database Objects Microsoft SQL Server – Applications using SQL Server 7.0 or later Oracle – Applications using Oracle data sources Object Linking and Embedding Database (OLE DB) – Common layer that can access many different database (including Oracle, SQLServer, Access, MySQL) through the use of connection libraries for each type of database Open Database Connectivity (ODBC) – An earlier layer for accessing many different database types

Microsoft Visual Studio Database Objects Visual Studio has separate libraries for each of the data types – SQL and Oracle layers are more “direct” than OLEDB – but – it locks in the database For the stuff I did in the past, I used OLEDB because the code I had accessed both Oracle and SQLServer databases. If you are for sure only going to support one database platform, (and it’s either Oracle or SQLServer), it would be better to use the one specific for that DBMS.

The FundFriend Database

Let’s Play With The Data Some simple single table queries – Probably the best we can do with this is against Account Let’s link the Account to Friends Let’s link the Account to the Transactions Let’s put them all together. OK – Not expecting you to get this in five minutes!! – All SQL for our Assignment 5 will be done for you.

A Basic Select Clause Let’s Use the Server Explorer in VS2012 SELECT field-names FROM table-name(s) WHERE condition clause

Accessing a Database through VS Manual Set-Up Classes Connection Class – Defines the type and location of the database Command Class – Used to define the command (Select, Insert, Update, Delete) that needs to be executed. DataReader Class – For Select statements, returns one record at a time so that it can be manipulated. DataAdapter Class – For Select statements, holds all records returned by the Select, and can be used to subsequently update the database (although I really don’t like that feature!!)

19 Connecting to the Database (Microsoft SQL Server) Add using directives – using System.Data.Sql; – using System.Data.SqlClient; Instantiate an object of connection class – Send connection string that includes the actual database provider and the data source (name of the database) string sConnection; sConnection Source=(LocalDB)\v11.0;AttachDbFilename=" + Application.StartupPath Security=True"; SqlConnection dbConn = new SqlConnection(sConnection); dbConn.Open();

Once Connected… Set up a Command Class to pass the SQL statements to the database management routines: dbCmd = new SqlCommand(); dbCmd.CommandText = sSQL; dbCmd.Connection = dbConn; For Update type commands, one would then Execute the command and it usually returns the number of records changed. int nRecordsChanged = dbCmd.ExecuteNonQuery()

Retrieving Data If you are retrieving data, you have two choices: – Record by record using a data Reader: dbReader = dbCmd.ExecuteReader(); while (dbReader.Read()) { // Do stuff with the data from the reader } dbReader.Close();

Retreiving Data Or, one can pull the entire result set from the query into a Dataset using a DataAdapter Class dbCmd.CommandText = sSQL; dbCmd.Connection = dbConn; dbTranAdapter = new SqlDataAdapter(); dbTranAdapter.SelectCommand = dbCmd; dbTranSet = new DataSet(); dbTranAdapter.Fill(dbTranSet, "Transactions");

Let’s Access The Data Through a Program Using the Manual Way

“Automated” Data Access in Visual Studio Windows Forms Data Aware Controls can be configured with database connections and SQL and kinda work by magic. – Not a fan because you lose a great deal of control, but will walk through this anyway in case you see this somewhere else. Includes – GridView, Combo Box, Details View

“Magical” database access Creating a “data source” Binding that data source with a data aware control Linking that to the SQL statements for retrieving and updating the data. I will now fail miserably and giving an example of this, but have one already done just in case!!

A Word About LINQ There is a big “disconnect” between application program and database access – The “standard” way of accessing data makes use of libraries that bride the gap between the program and the database But basically you are passing SQL strings to the DBMS and returning datasets that need to be interpreted Several other systems have tried to “Marry” programs to DBMSs. – Java uses JSQL, which basically is a pre-compiler that allows a program to code “SQL” statements are regular programming statements. – And old database access technique call PRO-C did a similar set-up for “C” programs – I have always moved the database calls out of the main program and into classes or web services so all of the crap you have to do is hidden from the main routines.

A Word About Linq With Visual Studio, Microsoft introduced their “Language Integrated Query” which allows a program to “connect” to a data source and then have the columnar information available for direct manipulation by the program. – What we have now requires us to convert the data to C# variables, and the convert it back when we update the database. Goods and Bads – Integration is nice, but it has a cost Some complex things you can do with SQL, you cannot do with LINQ Whatever LINQ looks like, it ends up being SQL, so it may not be as efficient as doing it by hand. But it does make the coding of a program more direct and concise. And it can be used for more than just databases.

Moving On Our Assignment 5 will be to develop a web based application that can run on a smart phone that implements a “PayPal” or “Bill Pay” System. The system will be based on our FundFriend database Tonight, we will do a quick design of what we need to incorporate into the system

FundFriend Web Application This week you must complete the basic screen designs for the system and turn them into Blackboard before next week (it would be tonight, but I’m guessing as I write this that several students won’t be here). That will be worth 3 points. Next week we will go over the basics of Web Development using VS and C#, and then mock up our design in ASP.NET forms. These form designs would then be turned in and will be worth 3 more points. The last week of class, we will do our best to add the actual code to the system to link the forms together and update the database. Whatever we get done that evening before the review will be worth 4 points. Each week I will have a “starting” point so that we are all on the same “page”.

Fund Friend What do we need?