FireDAC.IFDPhysConnection.Transactions Sample

This sample demonstrates the use of the IFDPhysTransaction interface to manage database transactions.

Location

You can find the Transactions sample project at:

• Start | Programs | Embarcadero RAD Studio Berlin | Samples and then navigate to:
  • Object Pascal\Database\FireDAC\Samples\Phys Layer\IFDPhysConnection\Transactions
• Subversion Repository:
  • Delphi: http://sourceforge.net/p/radstudiodemos/code/HEAD/tree/branches/RADStudio_Berlin/Object%20Pascal/Database/FireDAC/Samples/Phys%20Layer/IFDPhysConnection/Transactions

Description

The Transactions sample shows you how to use the IFDPhysTransaction interface to manage database transactions. To this end, the sample makes use of the following properties and methods of IFDPhysTransaction:

• The Isolation property, which is used for setting up the transaction isolation level for the transactions that FireDAC manages.
• The StartTransaction method, which is used to start a new database transaction.
• The Commit method, which is used to permanently store modifications made in the current transaction to the database.
• The Rollback method, which is used to cancel all modifications made in the current transaction to the database.

How to Use the Sample

1. Navigate to the location given above and open IFDPhys_Transactions.dproj.
2. Press F9 or choose Run > Run.

Files

File in Delphi	Contains
IFDPhys_Transactions.dproj IFDPhys_Transactions.dpr	The project itself.
fTransactions.pas fTransactions.fmx	The main form.

Implementation

When you run the application, clik the Use Connection Definition combo box and select an option in order to define a connection. When the connection is defined, the sample uses the CreateCommand method of IFDPhysConnection to create a command interface. Then, the sample implements the following database transaction features in run time:

Set up the transaction isolation level

The sample sets the Isolation property of IFDPhysTransaction to xiReadCommitted to allow the reading of committed (permanent) changes made to the database by other simultaneous transactions. This is the default value of the Isolation property.

Start a transaction

The sample uses the StartTransaction method to start a new database transaction. During the transaction, the sample uses the Prepare method of IFDPhysCommand to execute a DELETE command. The SQL command is the following: 'delete from {id FDQA_TransTable}'.

Commit the transaction

The sample uses the Commit method to permanently store modifications made in the current transaction to the database.

Rollback the transaction

The sample uses the Rollback method to cancel all the modifications made in the current transaction.

Note: The sample use this method if an exception is raised.

Uses

• IFDPhysConnection
  • CreateCommand
• IFDPhysCommand
  • Prepare
• IFDPhysTransaction
  • Isolation
  • StartTransaction
  • Commit
  • Rollback
• TComboBox
• TMemo

See Also

• FireDAC
• Defining Connection (FireDAC)
• Transactions
• Managing Transactions (FireDAC)
• Specifying the Transaction Isolation Level

Samples

• FireDAC TFDConnection Transactions sample