7.5.2.3 Delete a Data Row Using the UpdaTable ResultSet
In this section, we try to delete a faculty record from our Faculty Table using the UpdaTable ResultSet method. Perform the following operations to copy an existing project and make it our new project, OracleUpdaTableDelete:
- Copy the project OracleUpdaTableUpdate and change its name to OracleUpdaTable Delete.
- Save it to your default folder, ClassDB Projects\Chapter 7.
Double-click on the Delete button from the FacultyFrame Form window to open its event handler, and modify the code shown in Figure 7.25 to perform the data delete function using the UpdaTable ResultSet method.
Let’s have a closer look at this piece of modified code to see how it works.
A. First we add an if block to distinguish between the Java executeQuery Method and the Java UpdaTable ResultSet method to perform the data deletion action.
B. An else if block is added with the same objective as step A.
C. The query string is created, and it is used to help the UpdaTable ResultSet object do the data delete action. The point to be noted here is that a Table alias, f, is used to represent the Faculty Table and enable this query to retrieve all columns from that Table. You cannot directly use the star (*) to do this query since it is prohibited in this enhanced ResultSet.
D. A try-catch block is used to perform the data delete action. A PreparedStatement is created with two ResultSet parameters, TYPE _ SCROLL _ SENSITIVE and CONCUR _ UPDATable, to define the ResultSet object to enable it to be scrollable and updaTable and furthermore enable it to perform data manipulation.
E. The setString() method is used to initialize the positional parameter in the query string.
F. The executeQuery() method is called to perform this query and return the query result to a new created ResultSet object.
G. We need first to identify the location of the row to be deleted. In fact, there is only one row that has been retrieved from our Faculty Table and saved in the ResultSet, which is the selected faculty member to be removed, and this row will be deleted with the data delete action. Therefore, the absolute position for this row is 1.
H. The deleteRow() method is executed to delete this record from the ResultSet and the database. In fact, the data delete will not happen until the next Commit command is exe-cuted. Be aware that by default, the auto-commit flag is set to true so that any operational run is committed immediately.
I. The catch block is used to track and collect any possible exception for this data deletion.
J. Otherwise, if another method is selected by the user, a warning message is displayed to remind the user to select a valid method.
K. Finally, the user-defined method, CurrentFaculty(), is called to update the Faculty Name combo box to enable users to confirm this delete action later.
