How to use the Transaction function from mssql

mssql.Transaction is a class in the mssql library for creating and managing transactions when working with SQL Server databases in Node.js.

How does mssql.Transaction work?

The mssql.Transaction class is a part of the mssql library, which provides an interface for working with Microsoft SQL Server databases in Node.js. When you want to perform a series of related database operations, you can group them together into a transaction. A transaction is a series of database operations that are executed as a single unit of work. Either all of the operations in the transaction are executed, or none of them are. The mssql.Transaction class provides methods for creating and managing transactions. You can create a new transaction by calling the begin() method of a mssql.Connection object. The begin() method returns a new mssql.Transaction object that represents the transaction. Once you have a mssql.Transaction object, you can execute database operations within the transaction using the request() method of the mssql.Transaction object. The request() method returns a mssql.Request object that you can use to execute SQL statements and retrieve the results. You can commit the transaction by calling the commit() method of the mssql.Transaction object. This will save all of the changes made within the transaction to the database. If there is an error during the transaction, you can roll back the transaction by calling the rollback() method of the mssql.Transaction object. This will undo all of the changes made within the transaction. Overall, the mssql.Transaction class provides a way to group related database operations into a transaction, which allows you to ensure that either all of the operations are executed or none of them are. This can be useful when you need to perform multiple database operations as part of a single unit of work.

Ai Example

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const sql = require("mssql");

async function performTransaction() {
  try {
    // create a connection to the database
    const pool = await sql.connect(
      "mssql://username:password@localhost/database"
    );

    // start a transaction
    const transaction = new sql.Transaction(pool);
    await transaction.begin();

    try {
      // execute some SQL statements within the transaction
      await transaction
        .request()
        .input("productId", sql.Int, 1)
        .query("UPDATE Products SET Price = Price * 0.9 WHERE Id = @productId");

      await transaction
        .request()
        .input("customerId", sql.Int, 2)
        .query("UPDATE Customers SET Discount = 0.05 WHERE Id = @customerId");

      // commit the transaction
      await transaction.commit();

      console.log("Transaction committed successfully.");
    } catch (err) {
      // if there was an error, roll back the transaction
      await transaction.rollback();

      console.error("Transaction rolled back.", err);
    }
  } catch (err) {
    console.error("Error connecting to the database.", err);
  }
}

performTransaction();

In this example, we first create a connection to the database using the sql.connect() method of the mssql library. We then create a new mssql.Transaction object by calling the constructor with the pool object as the argument. We then call the begin() method of the mssql.Transaction object to start the transaction. Within the transaction, we execute two SQL statements using transaction.request().query(). These statements update the price of a product and the discount of a customer in the database. After the SQL statements have been executed, we call the commit() method of the mssql.Transaction object to commit the transaction. If there is an error during the transaction, we catch the error and call the rollback() method of the mssql.Transaction object to roll back the transaction. Overall, this example demonstrates how to use the mssql.Transaction class to create and manage a transaction when working with a SQL Server database in Node.js.