The Purpose Of A Dataset And How To Create One

The Purpose Of A Dataset And Describe How To Create A D

(TCO 4) Explain the purpose of a dataset and describe how to create a dataset called dsOrder in Visual Studio 2012. Assume you have the following function in the clsDataLayer class. Write the SQL command to select all rows from the tblOrder table, and write the code to fill the dataset.

public static dsOrder GetOrder(string Database) { dsOrder DS; OleDbConnection sqlConn; OleDbDataAdapter sqlDA; sqlConn = new OleDbConnection("PROVIDER=Microsoft.ACE.OLEDB.12.0;" + "Data Source=" + Database); // Write the code here to select all rows from the tblOrder table _______________________________________________________ DS = new dsOrder(); // Write the code here to populate the dataset ________________________________________________________ return DS; }

Paper For Above instruction

The purpose of a dataset in the context of database management and application development is to serve as an in-memory cache that holds data retrieved from a database, allowing for data manipulation, display, and updates within an application without immediate direct interaction with the database. Datasets are a critical component of ADO.NET, providing a disconnected data architecture that enhances efficiency and flexibility in handling data (Microsoft Docs, 2023). They store data in a tabular format, support relationships among tables, and enable developers to perform CRUD (Create, Read, Update, Delete) operations with minimal database connection overhead.

Creating a dataset such as dsOrder in Visual Studio 2012 involves several steps, typically guided by the Visual Studio designer tools and code generation features. First, a developer needs to add a new DataSet item to the project, which generates a class derived from DataSet. Within this dataset, tables like tblOrder are defined, either by manually configuring the schema or by using the visual designer connected to the database.

In the code snippet provided, the method GetOrder aims to establish a connection to the database using an OleDbConnection object and retrieve all data from the tblOrder table into the dsOrder dataset. The SQL command necessary to achieve this is a standard SELECT statement:

strSQL = "SELECT * FROM tblOrder";

This command fetches all the rows and columns from the tblOrder table. To populate the dsOrder dataset with this data, an OleDbDataAdapter must be instantiated with the SQL command and the connection object. The DataAdapter's Fill method is then used to load data into the dataset. The complete code for populating the dataset looks like this:

sqlDA = new OleDbDataAdapter(strSQL, sqlConn);

sqlDA.Fill(DS, "tblOrder");

Putting it all together, the method should be written as follows:

public static dsOrder GetOrder(string Database) {

dsOrder DS; 


OleDbConnection sqlConn; 


OleDbDataAdapter sqlDA; 


string strSQL = "SELECT * FROM tblOrder"; 


sqlConn = new OleDbConnection("PROVIDER=Microsoft.ACE.OLEDB.12.0;" + "Data Source=" + Database);


DS = new dsOrder();


sqlDA = new OleDbDataAdapter(strSQL, sqlConn);


sqlDA.Fill(DS, "tblOrder");


return DS; 


}

This approach ensures that the dsOrder dataset is populated with all records from the tblOrder table for further processing or display within the application.

Implementation of Transactions in Web Applications and SQL Commands

Implementing transactions in web applications is vital for maintaining data integrity, consistency, and reliability, especially when multiple related database operations need to be executed atomically. A transaction ensures that a series of database operations either all succeed or all fail as a unit, preventing partial updates that could lead to inconsistent data states (Elmasri & Navathe, 2015).

The SQL commands COMMIT and ROLLBACK are fundamental for transaction control. The COMMIT command is used to permanently save all changes made during a transaction, indicating that the operations have completed successfully (Kumar & Sahu, 2016). Conversely, ROLLBACK undoes all changes made during the current transaction if an error occurs, restoring the database to its previous consistent state.

In the context of the provided SaveEmployee function, transactions are used to ensure that inserting a new employee record is atomic. If the insert operation succeeds, the transaction is committed; if an exception occurs, the transaction is rolled back to leave the database unchanged. Here is how the code can be extended:

public static bool SaveEmployee(string Database, string FirstName, string LastName, string PayRate) {

bool recordSaved; 


OleDbTransaction myTransaction = null; 


OleDbConnection conn = new OleDbConnection("PROVIDER=Microsoft.ACE.OLEDB.12.0;" +"Data Source=" +Database);


try {


conn.Open();


myTransaction = conn.BeginTransaction();


OleDbCommand command = conn.CreateCommand();


string strSQL = "INSERT INTO tblEmployee (FirstName, LastName, PayRate) VALUES (?, ?, ?)";


command.Transaction = myTransaction; 


command.CommandType = CommandType.Text; 


command.CommandText = strSQL; 


command.Parameters.AddWithValue("?", FirstName);


command.Parameters.AddWithValue("?", LastName);


command.Parameters.AddWithValue("?", PayRate);


command.ExecuteNonQuery();


myTransaction.Commit(); // Commit the transaction


conn.Close();


recordSaved = true; 


} catch (Exception ex) {


if (myTransaction != null) {


myTransaction.Rollback(); // Rollback if error


}


conn.Close();


recordSaved = false; 


}


return recordSaved; 


}

This implementation guarantees data consistency by ensuring that either all the employee information is saved successfully or none at all, preserving the integrity of the database (Kumar & Sahu, 2016).

References

  • Elmasri, R., & Navathe, S. B. (2015). Fundamentals of Database Systems (7th ed.). Pearson.
  • Kumar, S., & Sahu, S. (2016). Transaction Management in Database Systems. International Journal of Computer Science and Information Technologies, 7(5), 512-515.
  • Microsoft Docs. (2023). Dataset Class (System.Data.DataSet) | Microsoft Learn. https://docs.microsoft.com/en-us/dotnet/api/system.data.dataset
  • Microsoft Docs. (2023). OleDbDataAdapter Class. https://docs.microsoft.com/en-us/dotnet/api/system.data.oledb.oledbdataadapter
  • Microsoft Docs. (2023). OleDbConnection Class. https://docs.microsoft.com/en-us/dotnet/api/system.data.oledb.oledbconnection
  • Elmasri, R., & Navathe, S. B. (2015). Fundamentals of Database Systems (7th ed.). Pearson.
  • Kumar, S., & Sahu, S. (2016). Transaction Management in Database Systems. International Journal of Computer Science and Information Technologies, 7(5), 512-515.
  • Coronel, C., & Morris, S. (2015). Database Systems: Design, Implementation, & Management (11th ed.). Cengage Learning.
  • Date, C. J. (2012). Database Design and Relational Theory: Normal Forms and All That Jazz. O'Reilly Media.
  • García-Molina, H., Ullman, J. D., & Widom, J. (2008). Database Systems: The Complete Book. Pearson.

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