Using Transaction Control Methods
You can explicitly control transactions through the following methods:
RWDBConnection::beginTransaction(const RWCString& savepoint = RWCString())
RWDBConnection::rollbackTransaction(const RWCString& savepoint = RWCString())
RWDBConnection::commitTransaction(const RWCString& savepoint = RWCString())
RWDBConnection::setSavepoint(const RWCString& savepoint)
These methods are implemented using the following Transact-SQL transaction statements:
"begin transaction [savepoint]"
"rollback transaction [savepoint]"
"commit transaction [savepoint]"
"save transaction savepoint"
An application can add the DB Interface Module transaction methods to its code to take explicit control of its transaction blocks. Transactions may be nested and the -savepoint feature is supported. The -savepoint feature allows a current transaction to be partially rolled back to a marked point.
NOTE: At the time of this writing, conflicting information was found in the MS SQL Server ODBC driver documentation regarding the use of -Transact‑SQL transaction statements. Please see the Microsoft SQL Server readme for more information regarding transaction savepoints.
The example below demonstrates the use of the savepoint feature and the other transaction processing methods of the DB Interface Module.
// Assume we have a table myTable(c int) with no rows in it.
RWDBInserter ins = myTable.inserter();
cn.beginTransaction("outmost"); // Begin transaction.
// Transaction name is allowed.
// Note: unlike savepoint name,
// transaction name is not used
// by server.
ins << 1).execute(cn); // First insertion
cn.beginTransaction("inner"); // Nested transaction begins
...
cn.setSavepoint("svp1"); // Save first insertion
(ins << 2).execute(cn); // Second insertion
(ins << 3).execute(cn); // Third insertion
cn.rollbackTransaction("svp1"); // Roll back second and
// third insertions.
cn.commitTransaction("inner"); // Pairing inner transaction
cn.commitTransaction("outmost"); // Commit transaction on
// part that is not rolled back.
// The above program results in myTable holding one row of data.
// Its value is 1.
