New sample application that shows how to use "instead of" triggers to support updatable views.

h2/src/docsrc/help/help.csv

@@ -605,6 +605,7 @@ Exceptions that occur within such triggers are ignored.
 
 INSTEAD OF triggers are implicitly row based and behave like BEFORE triggers.
 Only the first such trigger is called. Such triggers on views are supported.
+They can be used to make views updatable.
 
 The MERGE statement will call both INSERT and UPDATE triggers.
 Not supported are SELECT triggers with the option FOR EACH ROW,
@@ -645,6 +646,8 @@ dependent views will not need to be recreated. If dependent views will become
 invalid as a result of the change an error will be generated, but this error
 can be ignored if the FORCE clause is also used.
 
+Views are not updatable except when using 'instead of' triggers.
+
 Admin rights are required to execute this command.
 This command commits an open transaction.
 ","

h2/src/docsrc/html/changelog.html

@@ -18,7 +18,8 @@ Change Log
 <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
-<ul><li>H2 Console: opening a MS SQL Server database is now faster.
+<ul><li>New sample application that shows how to use "instead of" triggers to support updatable views.
+</li><li>H2 Console: opening a MS SQL Server database is now faster.
     Also, listing the database meta data sometimes resulted in an exception.
 </li><li>Linked tables / MS SQL Server: if the tables were created in mixed case in MS SQL Server, 
     then the identifiers in the linked tables were case sensitive (in H2).

h2/src/test/org/h2/samples/UpdatableView.java

+/*
+ * Copyright 2004-2011 H2 Group. Multiple-Licensed under the H2 License,
+ * Version 1.0, and under the Eclipse Public License, Version 1.0
+ * (http://h2database.com/html/license.html).
+ * Initial Developer: H2 Group
+ */
+package org.h2.samples;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import org.h2.tools.TriggerAdapter;
+
+/**
+ * This sample application shows how to use triggers to create updatable views.
+ */
+public class UpdatableView extends TriggerAdapter {
+
+    private PreparedStatement prepDelete, prepInsert;
+
+    /**
+     * This method is called when executing this sample application from the
+     * command line.
+     *
+     * @param args the command line parameters
+     */
+    public static void main(String... args) throws Exception {
+        Class.forName("org.h2.Driver");
+        Connection conn = DriverManager.getConnection("jdbc:h2:mem:");
+        Statement stat;
+        stat = conn.createStatement();
+
+        // create the table and the view
+        stat.execute("create table test(id int primary key, name varchar)");
+        stat.execute("create view test_view as select * from test");
+
+        // create the trigger that is called whenever
+        // the data in the view is modified
+        stat.execute("create trigger t_test_view instead of " +
+                "insert, update, delete on test_view for each row " +
+                "call \"" + UpdatableView.class.getName() + "\"");
+
+        // test a few operations
+        stat.execute("insert into test_view values(1, 'Hello'), (2, 'World')");
+        stat.execute("update test_view set name = 'Hallo' where id = 1");
+        stat.execute("delete from test_view where id = 2");
+
+        // print the contents of the table and the view
+        System.out.println("table test:");
+        ResultSet rs;
+        rs = stat.executeQuery("select * from test");
+        while (rs.next()) {
+            System.out.println(rs.getInt(1) + " " + rs.getString(2));
+        }
+        System.out.println();
+        System.out.println("test_view:");
+        rs = stat.executeQuery("select * from test_view");
+        while (rs.next()) {
+            System.out.println(rs.getInt(1) + " " + rs.getString(2));
+        }
+
+        conn.close();
+    }
+
+    public void init(Connection conn, String schemaName, String triggerName,
+            String tableName, boolean before, int type) throws SQLException {
+        prepDelete = conn.prepareStatement("delete from test where id = ?");
+        prepInsert = conn.prepareStatement("insert into test values(?, ?)");
+        super.init(conn, schemaName, triggerName, tableName, before, type);
+    }
+
+    public void fire(Connection conn, ResultSet oldRow, ResultSet newRow) throws SQLException {
+        if (oldRow != null && oldRow.next()) {
+            prepDelete.setInt(1, oldRow.getInt(1));
+            prepDelete.execute();
+        }
+        if (newRow != null && newRow.next()) {
+            prepInsert.setInt(1, newRow.getInt(1));
+            prepInsert.setString(2, newRow.getString(2));
+            prepInsert.execute();
+        }
+    }
+
+}

h2/src/test/org/h2/test/unit/TestSampleApps.java

@@ -76,6 +76,8 @@ public class TestSampleApps extends TestBase {
         // process)
         testApp("The sum is 20.00", org.h2.samples.TriggerSample.class);
         testApp("Hello: 1\nWorld: 2", org.h2.samples.TriggerPassData.class);
+        testApp("table test:\n1 Hallo\n\ntest_view:\n1 Hallo",
+                org.h2.samples.UpdatableView.class);
         testApp(
                 "adding test data...\n" +
                 "defrag to reduce random access...\n" +