//*************************************************************************** // (c) Copyright IBM Corp. 2007 All rights reserved. // // The following sample of source code ("Sample") is owned by International // Business Machines Corporation or one of its subsidiaries ("IBM") and is // copyrighted and licensed, not sold. You may use, copy, modify, and // distribute the Sample in any form without payment to IBM, for the purpose of // assisting you in the development of your applications. // // The Sample code is provided to you on an "AS IS" basis, without warranty of // any kind. IBM HEREBY EXPRESSLY DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR // IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF // MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Some jurisdictions do // not allow for the exclusion or limitation of implied warranties, so the above // limitations or exclusions may not apply to you. IBM shall not be liable for // any damages you suffer as a result of using, copying, modifying or // distributing the Sample, even if IBM has been advised of the possibility of // such damages. //*************************************************************************** // // SOURCE FILE NAME: TbGenCol.java // // SAMPLE: How to use generated columns // // This sample demonstrates how to use generated columns. // It first creates a table and populates it with some data. // Then, the integrity of the table is set to off and a // generated column is added to the table. The integrity of // the table is then set to IMMEDIATE CHECKED FORCE GENERATED // to refresh the values of the newly added column. Finally, // an index is created on the generated column to illustrate // how they can be used to improve query performance. The // sample drops the table it created before exiting. // // SQL STATEMENTS USED: // CREATE TABLE // INSERT // SELECT // SET INTEGRITY // ALTER TABLE // CREATE INDEX // DROP TABLE // // Classes used from Util.java are: // Db // Data // JdbcException // // // Output will vary depending on the JDBC driver connectivity used. //*************************************************************************** // // For more information on the sample programs, see the README file. // // For information on developing Java applications see the Developing Java Applications book. // // For information on using SQL statements, see the SQL Reference. // // For the latest information on programming, compiling, and running DB2 // applications, visit the DB2 Information Center at // http://publib.boulder.ibm.com/infocenter/db2luw/v9r7/index.jsp //**************************************************************************/ import java.lang.*; import java.sql.*; class TbGenCol { public static void main(String argv[]) { try { Db db = new Db(argv); System.out.println(); System.out.println("THIS SAMPLE SHOWS HOW TO USE GENERATED COLUMNS."); // connect to the 'sample' database db.connect(); createTableWithData(db.con); addGeneratedColumntoTable(db.con); createIndexOnGeneratedCol(db.con); dropTable(db.con); // disconnect from the 'sample' database db.disconnect(); } catch (Exception e) { JdbcException jdbcExc = new JdbcException(e); jdbcExc.handle(); } } // main // Helping function: This function display the content of the table // 'genColClassSchedule'. static void tbContentDisplay(Connection con, boolean columnadded) { try { Integer c_id = new Integer(0); String c_name = null; String type = null; String days = null; String starting = null; String ending = null; Integer duration = new Integer(0); System.out.println(); System.out.println( " SELECT * FROM genColClassSchedule"); if (columnadded) { System.out.println( " " + "C_ID C_NAME TYPE DAYS STARTING ENDING DURATION\n" + " " + "---- ------------- ----- ----- --------- --------- --------"); } else { System.out.println( " C_ID C_NAME TYPE DAYS STARTING ENDING\n" + " ---- ------------- ----- ----- --------- ---------"); } Statement stmt = con.createStatement(); ResultSet rs = stmt.executeQuery( "SELECT * FROM genColClassSchedule"); while (rs.next()) { c_id = Integer.valueOf(rs.getString(1)); c_name = rs.getString(2); type = rs.getString(3); days = rs.getString(4); starting = rs.getString(5); ending = rs.getString(6); if (columnadded) { duration = Integer.valueOf(rs.getString(7)); } System.out.print(" "+ Data.format(c_id, 4) + " " + " " + Data.format(c_name, 13) + " " + Data.format(type, 5) + " " + Data.format(days, 5) + " " + Data.format(starting, 9) + " " + Data.format(ending, 9)); if (columnadded) { System.out.println(" " + Data.format(duration, 8)); } else { System.out.println(); } } System.out.println(); rs.close(); stmt.close(); } catch (Exception e) { JdbcException jdbcExc = new JdbcException(e, con); jdbcExc.handle(); } } // tbContentDisplay // Helping function: This function creates a table called // 'genColClassSchedule' and inserts some data into the table. static void createTableWithData(Connection con) { try { System.out.println(); System.out.println( "----------------------------------------------------------\n" + "USE THE SQL STATEMENTS:\n" + " CREATE TABLE\n" + " INSERT INTO\n" + "TO CREATE A TABLE WITH DATA"); System.out.println(); System.out.println( " CREATE TABLE genColClassSchedule(\n" + " c_id int,\n"+ " c_name varchar(20),\n"+ " type varchar(3),\n"+ " days varchar(3),\n"+ " start time,\n"+ " end time)\n"); Statement stmt = con.createStatement(); stmt.execute( "CREATE TABLE genColClassSchedule(c_id int," + " c_name varchar(20),"+ " type varchar(3)," + " days varchar(3)," + " start time," + " end time)"); System.out.println( " INSERT INTO genColClassSchedule \n" + " VALUES (10,'CMPUT 391','LEC','MWF','14:00:00','14:50:00'),\n" + " (20,'ENGLISH 101','LEC','MWF','08:00:00','08:50:00'),\n" + " (30,'MATH 117','LEC','TR','11:00:00','12:20:00'),\n" + " (40,'CMPUT 391','LAB','T','14:00:00','16:50:00'),\n" + " (50,'PHYS 102','LEC','MWF','09:00:00','09:50:00')"); stmt.executeUpdate( "INSERT INTO genColClassSchedule " + "VALUES (10,'CMPUT 391','LEC','MWF','14:00:00','14:50:00'), " + "(20,'ENGLISH 101','LEC','MWF','08:00:00','08:50:00'), " + "(30,'MATH 117','LEC','TR','11:00:00','12:20:00'), " + "(40,'CMPUT 391','LAB','T','14:00:00','16:50:00'), " + "(50,'PHYS 102','LEC','MWF','09:00:00','09:50:00')"); stmt.close(); con.commit(); tbContentDisplay(con,false); } catch (Exception e) { JdbcException jdbcExc = new JdbcException(e, con); jdbcExc.handle(); } } // createTableWithData // This function adds a generated column called 'duration' to the table. static void addGeneratedColumntoTable(Connection con) { try { System.out.println( "----------------------------------------------------------\n" + "USE THE SQL STATEMENTS:\n" + " ALTER TABLE\n" + "TO ADD A GENERATED COLUMN INTO A TABLE"); System.out.println(); System.out.println(" SET INTEGRITY FOR genColClassSchedule OFF\n"); Statement stmt = con.createStatement(); stmt.execute("SET INTEGRITY FOR genColClassSchedule OFF"); // the expression (60*hour(end-start)+minute(end-start)) converts // the decimal result of time arithmetic into minutes System.out.println( " ALTER TABLE genColClassSchedule\n" + " ADD COLUMN DURATION INTEGER\n" + " GENERATED ALWAYS AS (60*hour(end-start)+minute(end-start))\n"); stmt.execute("ALTER TABLE genColClassSchedule " + "ADD COLUMN DURATION INTEGER " + "GENERATED ALWAYS AS " + "(60*hour(end-start)+minute(end-start))"); System.out.println( " SET INTEGRITY FOR genColClassSchedule\n"+ " IMMEDIATE CHECKED FORCE GENERATED"); stmt.execute("SET INTEGRITY FOR genColClassSchedule " + "IMMEDIATE CHECKED FORCE GENERATED"); stmt.close(); con.commit(); tbContentDisplay(con,true); } catch (Exception e) { JdbcException jdbcExc = new JdbcException(e, con); jdbcExc.handle(); } } // addGeneratedColumntoTable // This function creates an index on the generated column static void createIndexOnGeneratedCol(Connection con) { try { System.out.println( "----------------------------------------------------------\n" + "USE THE SQL STATEMENTS:\n" + " CREATE INDEX\n" + "TO CREATE AN INDEX ON THE GENERATED COLUMN"); System.out.println(); System.out.println( " CREATE INDEX duration_index\n" + " ON genColClassSchedule (duration)\n"); Statement stmt = con.createStatement(); stmt.execute("CREATE INDEX duration_index " + "ON genColClassSchedule (duration)"); System.out.println( " SELECT * from genColClassSchedule\n" + " WHERE (60*hour(end-start)+minute(end-start)) > 60"); System.out.println( " " + "C_ID C_NAME TYPE DAYS STARTING ENDING DURATION\n" + " " + "---- ------------- ----- ----- --------- --------- --------"); ResultSet rs = stmt.executeQuery("SELECT * from genColClassSchedule " + "WHERE (60*hour(end-start)" + " + minute(end-start)) > 60"); Integer c_id = new Integer(0); String c_name = null; String type = null; String days = null; String starting = null; String ending = null; Integer duration = new Integer(0); while (rs.next()) { c_id = Integer.valueOf(rs.getString(1)); c_name = rs.getString(2); type = rs.getString(3); days = rs.getString(4); starting = rs.getString(5); ending = rs.getString(6); duration = Integer.valueOf(rs.getString(7)); System.out.println(" "+ Data.format(c_id, 4) + " " + " " + Data.format(c_name, 13) + " " + Data.format(type, 5) + " " + Data.format(days, 5) + " " + Data.format(starting, 9) + " " + Data.format(ending, 9) + " " + Data.format(duration, 8)); } rs.close(); stmt.close(); System.out.println(); System.out.println( " NOTE:\n" + " Indexes can be created on generated columns to improve query\n"+ " performance. If a query predicate contains a clause identical\n"+ " to the clause used to define the generated column and the\n"+ " generated column is indexed, the optimizer will use the index.\n"+ " The SELECT query:\n\n"+ " SELECT * FROM genColClassSchedule\n" + " WHERE (60*hour(end-start)+minute(end-start)) > 60\n\n" + " will, in general, perform better using the indexed generated\n" + " column than without it. The idea is to add expressions that\n" + " occur frequently in queries as generated columns and then\n" + " index them to improve query performance."); con.commit(); } catch (Exception e) { JdbcException jdbcExc = new JdbcException(e, con); jdbcExc.handle(); } } // createIndexOnGeneratedCol // Helping function: This function drops the table created by this program static void dropTable(Connection con) { try { System.out.println(); System.out.println( "----------------------------------------------------------\n" + "USE THE SQL STATEMENTS:\n" + " DROP TABLE\n" + "TO DROP A TABLE"); System.out.println(); System.out.println(" DROP TABLE genColClassSchedule"); Statement stmt = con.createStatement(); stmt.execute("DROP TABLE genColClassSchedule"); stmt.close(); con.commit(); } catch (Exception e) { JdbcException jdbcExc = new JdbcException(e, con); jdbcExc.handle(); } } // dropTable } // TbGenCol