About Question enthuware.ocpjp.v8.2.1196 :

[schchen2000]

c.rollback(sp1); // passing the Savepoint variable here

Had we passed sp1 into the rollback(), we would have only lost the 1st record insertion.

We would have counted the 2nd insertion and therefore our final answer would have been 3 instead of 2.

Is that correct? Many thanks.

Schmichael

[admin]

Could you please post complete code that you want to discuss? Without that, it is difficult to figure out the changes you are trying to make to code that is given with the question.

-Paul.

[schchen2000]

Code: Select all

Assuming that the table student2 does not have any row, how many rows will be present in this table after the following code is executed?          

try (Connection c = DriverManager.getConnection("jdbc:derby://localhost:1527/sample", "app", "app");){
	c.setAutoCommit(false);
	Statement stmt = c.createStatement();
	int a1 = stmt.executeUpdate("insert into STUDENT2 values (1, 'aaa', 1.1)");
	Savepoint sp1 = c.setSavepoint();
	int a2 = stmt.executeUpdate("insert into STUDENT2 values (2, 'bbb', 2.1)");

	******c.rollback(sp1);***** <--- pass sp1 to rollback

	int a3 = stmt.executeUpdate("insert into STUDENT2 values (3, 'ccc', 3.1)");
	c.setAutoCommit(true);
	int a4 = stmt.executeUpdate("insert into STUDENT2 values (4, 'ddd', 4.1)");
}catch (SQLException e){
	e.printStackTrace();
}

[admin]

Assuming that you are trying to change the code as shown above, the call to rollback will roll back the row inserted by int a2 = stmt.executeUpdate("insert into STUDENT2 values (2, 'bbb', 2.1)");
So finally, the table should have records for 1, 3, and 4.

[schchen2000]

Assuming that you are trying to change the code as shown above, the call to rollback will roll back the row inserted by int a2 = stmt.executeUpdate("insert into STUDENT2 values (2, 'bbb', 2.1)");
So finally, the table should have records for 1, 3, and 4.

Thanks for the reply.

Schmichael

[jme_chg]

By the way, what would happen if we replaced:

int a4 = stmt.executeUpdate("insert into STUDENT2 values (4, 'ddd', 4.1)");

with:

int a4 = stmt.executeUpdate("insert into STUDENT2 values (3, 'ddd', 4.1)");

would there be an SQLException or would the row with primary key 3 be overwritten?

[admin]

An insert query tries to insert a new row and if a row by the same pk exists, the db will reject the query and you will end up with an SQLException in the java code.
You can try it out with JavaDB that comes bundled with IDEs such as NetBeans.