MacLochlainns Weblog

It’s amazing the moving parts in Oracle Database 11g, and the ones that I don’t use after installation for a while often reach out to teach me something new. That’s what happened when I went to launch SQL Developer on my Windows 7 Professional 64-bit installation.

I got the message Unable to find a Java Virtual Machine, as shown in the image below. It really means unable to find a 32-bit Java 5 or Java 6 (1.6.0_4+) SDK home. Although the installation appeared fine, it pointed the SQL Developer configuration file to an incompatible 64-bit Java 7 SDK.

You fix this error by following these steps:

1. Open the sqldeveloper.conf file and check the SetJavaHome parameter value. You find the sqldeveloper.conf file in the following directory:

%ORACLE_HOME\sqldeveloper\sqldeveloper\bin

2. Install the 32-bit Java 6 (1.6.0_4+) SDK on the operating system if not installed already. You can check whether it’s installed by looking for it in the Program Files (x86) folder.
3. Change the value of the SetJavaHome parameter to point to the new 32-bit Java 6 home directory (or folder). The following change to line 18 in the sqldeveloper.conf file should fix it on your installation (provided that’s your version of the JVM).

18

SetJavaHome C:\Program Files (x86)\Java\jdk1.6.0_34

Hope this helps those who run into the same issue.

I’m posting this because of a question raised against this older post on how to configure the %CLASSPATH% to find the ojdbc6.jar file. This is the lab file I use in my Database 1 class to expose students to the moving parts of writing Java programs against the Oracle database. That’s why I choose to use a CLOB data type, which requires Oracle’s DBMS_LOB package and wrapping stored procedures.

If you want the same content for MySQL, here’s the link. The full program in either blog entry is available by clicking on the fold/unfold Java Source Code Program widget at the bottom of the respective posts.

This demonstrates how to create an Java infrastructure for reading and writing large text files to an Oracle database. The example provides:

• A FileIO.jar library that lets you enter Oracle connection parameters through a JOptionPane, and a customized JFileChooser to filter and read source files from the file system.
• A ojdbc6.jar file, which is Oracle’s library for JDBC communication with the Oracle Databases.

The steps to compiling and testing this code are qualified below:

1. Download and install the Java Software Development Kit (JSDK) for Java 6.
2. Create a C:\JavaTest folder on Windows, or a /JavaTest directory from some mount point of your choice.
3. Download and position the ojdbc6.jar and FileIO.jar files in the JavaTest directory.
4. Create a batch file to source your environment path (%PATH% on Windows and $PATH on Linux or Mac OS X) and the two Java Archive (JAR) files. A sample batch file is noted below:

set PATH=C:\Program Files\Java\jdk1.6.0_07\bin;%PATH%
set CLASSPATH=C:\JavaDev\Java6\ojdbc6.jar;C:\JavaDev\Java6\FileIO.jar;.

You can run this file by simply typing the files first name. On Linux or Mac OS X, you first need to grant it privileges with the chmod command as 755.

5. Copy the WriteReadCLOB.java code from the bottom of this posting and also put it into the JavaTest directory.
6. Compile the WriteReadCLOB.java source code with the javac utility, as shown below:

javac WriteReadCLOB.java

After you compile it, you should run it as follows:

java WriteReadCLOB

7. Before running the code, you’ll need to seed (INSERT) a row that meets the desired hard coded criteria. It requires an ITEM_TITLE value of 'The Lord of the Rings - Fellowship of the Ring' and an ITEM_SUBTITLE of 'Widescreen Edition' in the ITEM table.
8. When it runs, you’ll see the following tabbed JOptionPane.

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// --------------------------------------------------------------------
// WriteReadCLOB.java
// by Michael McLaughlin
//
// This code demonstrates reading a large text file and displaying
// the text stream in a JLabel in a JFrame.
//
// The UPDATE and SELECT statements have dependencies on the
// create_store.sql script.
// --------------------------------------------------------------------
 
// Java Application class imports.
import java.awt.Dimension;
import java.awt.Font;
import java.awt.GridLayout;
import java.io.Reader;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
 
// Generic JDBC imports.
import java.sql.CallableStatement;
import java.sql.Clob;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
 
// Oracle JDBC import.
import oracle.jdbc.driver.OracleDriver;
import oracle.jdbc.pool.OracleDataSource;
 
// Include book libraries (available at publisher website).
import plsql.jdbc.DataConnectionPane;
import plsql.fileio.FileIO;
// -------------------------------------------------------------------/
public class WriteReadCLOB extends JFrame {
  // Define database connections.
  private String host;
  private String port;
  private String dbname;
  private String userid;
  private String passwd;
 
  // Define data connection pane.
  private DataConnectionPane message = new DataConnectionPane();
 
  // Construct the class.
  public WriteReadCLOB (String s) {
    super(s);
 
    // Get database connection values or exit.
    if (JOptionPane.showConfirmDialog(this,message
          ,"Set Oracle Connection String Values"
          ,JOptionPane.OK_CANCEL_OPTION) == 0) {
 
      // Set class connection variables.
      host = message.getHost();
      port = message.getPort();
      dbname = message.getDatabase();
      userid = message.getUserID();
      passwd = message.getPassword();
 
      // Print connection to console (debugging tool).
      message.getConnection();
 
      // Create a JPanel for data display.
      ManageCLOB panel = new ManageCLOB();
 
      // Configure the JPanel.
      panel.setOpaque(true);
      setContentPane(panel);
 
      // Configure the JFrame.
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setLocation(100,100);
      pack();
      setVisible(true); }
    else
      System.exit(1); }
  // -------------------------------------------------------------------/
  private class ManageCLOB extends JPanel {
 
    // Define display variables.
    private String clobText;
    private JScrollPane scrollPane;
    private JTextArea textArea;
    // -----------------------------------------------------------------/
    public ManageCLOB () {
      // Set layout manager.
      super(new GridLayout(1,0));
 
      // Assign file read to String.
      clobText = FileIO.openFile(FileIO.findFile(this));
 
      // Insert record before querying it.
      if (clobText.length() > 0) {
        if (insertClob(host,port,dbname,userid,passwd,clobText))
          clobText = getQuery(host,port,dbname,userid,passwd);
        else
          clobText = null; }
      else
        System.exit(2);
 
      // Construct text area and format it.
      textArea = new JTextArea(clobText);
      textArea.setEditable(false);
      textArea.setFont(new Font(Font.SANS_SERIF,Font.PLAIN,14));
      textArea.setLineWrap(true);
      textArea.setRows(10);
      textArea.setSize(400,100);
      textArea.setWrapStyleWord(true);
 
      // Put the image in container, and add label to panel.
      scrollPane = new JScrollPane(textArea);
      add(scrollPane); }
    // ---------------------------------------------------------------/
    private Boolean insertClob(String host,String port,String dbname
                              ,String user,String pswd,String fileString) {
 
      try
      {
        // Set the Pooled Connection Source
        OracleDataSource ods = new OracleDataSource();
        String url = "jdbc:oracle:thin:@//"+host+":"+port+"/"+dbname;
        ods.setURL(url);
        ods.setUser(userid);
        ods.setPassword(passwd);
 
        // Define connection.
        Connection conn = ods.getConnection();
 
        // Create statement.
        CallableStatement stmt =
          conn.prepareCall("UPDATE item "+
                           "SET    item_desc = ? "+
                           "WHERE  item_title = "+
                           "'The Lord of the Rings - Fellowship of the Ring'"+
                           "AND    item_subtitle = 'Widescreen Edition'");
 
        // Set string into statement.
        stmt.setString(1,fileString);
 
        // Execute query.
        if (stmt.execute())
          conn.commit();
 
        // Close resources.
        stmt.close();
        conn.close();
 
        // Return CLOB as a String data type.
        return true; } // End of connection try-block.
 
      catch (SQLException e) {
        if (e.getSQLState() == null) {
          System.out.println(
            new SQLException("Oracle Thin Client Net8 Connection Error.",
                             "ORA-" + e.getErrorCode() +
                             ": Incorrect Net8 thin client arguments:\n\n" +
                             "  host name     [" + host + "]\n" +
                             "  port number   [" + port + "]\n" +
                             "  database name [" + dbname + "]\n"
                             , e.getErrorCode()).getSQLState());
 
          // Return an empty String on error.
          return false; }
        else {
          System.out.println(e.getMessage());
 
          // Return an empty String on error.
          return false; }}}
    // -----------------------------------------------------------------/
    private String getQuery(String host,String port,String dbname
                           ,String user,String pswd) {
 
      // Define method variables.
      char[] buffer;
      int count = 0;
      int length = 0;
      String data = null;
      String[] type;
      StringBuffer sb;
 
      try {
        // Set the Pooled Connection Source
        OracleDataSource ods = new OracleDataSource();
        String url = "jdbc:oracle:thin:@//"+host+":"+port+"/"+dbname;
        ods.setURL(url);
        ods.setUser(userid);
        ods.setPassword(passwd);
 
        // Define connection.
        Connection conn = ods.getConnection();
 
        // Define metadata object.
        DatabaseMetaData dmd = conn.getMetaData();
 
        // Create statement.
        Statement stmt = conn.createStatement();
 
        // Execute query.
        ResultSet rset =
          stmt.executeQuery(
            "SELECT item_desc " +
            "FROM   item " +
            "WHERE  item_title = " +
            "'The Lord of the Rings - Fellowship of the Ring'"+
            "AND    item_subtitle = 'Widescreen Edition'");
 
        // Get the query metadata, size array and assign column values.
        ResultSetMetaData rsmd = rset.getMetaData();
        type = new String[rsmd.getColumnCount()];
        for (int col = 0;col < rsmd.getColumnCount();col++)
          type[col] = rsmd.getColumnTypeName(col + 1);
 
        // Read rows and only CLOB data type columns.
        while (rset.next()) {
          for (int col = 0;col < rsmd.getColumnCount();col++) {
            if (type[col] == "CLOB") {
              // Assign result set to CLOB variable.
              Clob clob = rset.getClob(col + 1);
 
              // Check that it is not null and read the character stream.
              if (clob != null) {
                Reader is = clob.getCharacterStream();
 
                // Initialize local variables.
                sb = new StringBuffer();
                length = (int) clob.length();
 
                // Check CLOB is not empty.
                if (length > 0) {
 
                  // Initialize control structures to read stream.
                  buffer = new char[length];
                  count = 0;
 
                  // Read stream and append to StringBuffer.
                  try {
                    while ((count = is.read(buffer)) != -1)
                      sb.append(buffer);
 
                    // Assign StringBuffer to String.
                    data = new String(sb); }
                  catch (Exception e) {} }
                else
                  data = (String) null; }
              else
                data = (String) null; }
            else {
              data = (String) rset.getObject(col + 1); }}}
 
        // Close resources.
        rset.close();
        stmt.close();
        conn.close();
 
        // Return CLOB as a String data type.
        return data; }
      catch (SQLException e) {
        if (e.getSQLState() == null) {
          System.out.println(
            new SQLException("Oracle Thin Client Net8 Connection Error.",
                             "ORA-" + e.getErrorCode() +
                             ": Incorrect Net8 thin client arguments:\n\n" +
                             "  host name     [" + host + "]\n" +
                             "  port number   [" + port + "]\n" +
                             "  database name [" + dbname + "]\n"
                             , e.getErrorCode()).getSQLState());
 
          // Return an empty String on error.
          return data; }
        else {
          System.out.println(e.getMessage());
          return data; }}
        finally {
          if (data == null) System.exit(1); }}}
  // -----------------------------------------------------------------/
  public static void main(String[] args) {
    // Define window.
    WriteReadCLOB frame = new WriteReadCLOB("Write & Read CLOB Text"); }}

Six years ago, I wrote Oracle Database 10g Express Edition PHP Web Programming for the release of the express edition. It was a lot of fun to write because I enjoy the PHP programming language, but unfortunately sales didn’t measure up too well. That’s probably because the population of PHP developers working with Oracle was small.

Today it seems there are more PHP developers working with Oracle 11g. While the population of PHP community for Oracle 11g is still smaller than for MySQL, it continues to grow year-over-year.

The FREE Underground PHP and Oracle Manual can help those converting PHP to run in the Oracle Call Interface, which is the replacement for MySQLi Interface. Chris Jones (an Oracle Open Source Product Manager) and Alison Holloway (an Oracle Senior Product Manager) write and maintain this book. It’s a great place to start if you’re migrating to Oracle Database 11g from MySQL.

In my database class, students write solutions as group exercises against the Oracle 11g XE database and then they port the solution individually to the MySQL 5.5 database. One of the students copied over a query like the one below to MySQL (a query used to track the expected number of row returns).

SELECT   COUNT(*)
FROM    (SELECT   DISTINCT
                  k.kingdom_id
         ,        kki.kingdom_name
         ,        kki.population
         FROM     kingdom_knight_import kki LEFT JOIN kingdom k
         ON       kki.kingdom_name = k.kingdom_name
         AND      kki.population = k.population);

It got an error they didn’t understand:

ERROR 1248 (42000): Every derived TABLE must have its own alias

Providing a dt query alias fixes the problem in MySQL for the following query. The fact that it was just an alias was a revelation to the student. That’s because Oracle databases don’t require aliases for inline views (what Oracle calls MySQL derived tables and Microsoft calls a Common Table Expression (CTE)).

SELECT   COUNT(*)
FROM    (SELECT   DISTINCT
                  k.kingdom_id
         ,        kki.kingdom_name
         ,        kki.population
         FROM     kingdom_knight_import kki LEFT JOIN kingdom k
         ON       kki.kingdom_name = k.kingdom_name
         AND      kki.population = k.population) dt;

MySQL requires that every derived table have its own alias. This make sense when you think about query optimization engines work, but that’s a story for a much longer post.

You can find more about inline views, derived tables, and common table expressions in this older post of mine. This post was promised so that future students can simply google and answer rather than ask me or a class tutor.

Somebody wanted to understand why you can backquote a single wildcard operator (that’s the underscore _ character) in MySQL, but can’t in Oracle. The answer is you can in Oracle when you know that you required an additional clause.

While I prefer using regular expression resolution, the LIKE operator is convenient. Here’s an example of backquoting an underscore in MySQL, where it looks for any string with an underscore anywhere in the string:

SELECT   common_lookup_type
FROM     common_lookup
WHERE    common_lookup_type LIKE '%\_%';

You can gain the same behavior in Oracle by appending the ESCAPE '\' clause, like this:

SELECT   common_lookup_type
FROM     common_lookup
WHERE    common_lookup_type LIKE '%\_%' ESCAPE '\';

The ESCAPE '\' clause is one of those Oracle details that often gets lost. It only works when the SQL*Plus ESCAPE parameter is set to OFF.

The SQL*Plus ESCAPE parameter default value is a backslash. and when the ESCAPE parameter is enabled a statement like this raises the following exception:

ERROR at line 3:
ORA-01425: escape CHARACTER must be CHARACTER string OF LENGTH 1

If you drop the ESCAPE '\' clause with the ESCAPE parameter enabled it will return all rows from the table not just those strings with an underscore in the string. Hope this helps if need to look for an underscore in a table.

A question posed by a student: “Why are Oracle Native Dynamic SQL (NDS) USING clause parameters IN, IN OUT, or OUT when the RETURNING INTO clause manages output values?” It a great question, isn’t it? The followup question was also great, “How do you implement an example of NDS IN OUT parameters?”

The answer is two fold. First, you should use the USING clause for parameter list input values and the RETURNING INTO clause for return values whenever possible. Second, when it’s not possible you’re generally passing parameters into and out of an NDS PL/SQL anonymous block.

The basic prototype for passing and retrieving values from an NDS statement is:

EXECUTE IMMEDIATE sql_stmt
  USING { IN | IN OUT | OUT } local_variable [, ...]
  RETURNING INTO { IN OUT | OUT } local_variable [, ...];

A quick and hopefully fun example is this parody on Marvel’s The Avengers. The program creates an anonymous block with a super hero of Thor and super villain of Loki, then it uses a USING clause with IN OUT parameters to an anonymous block statement. That’s basically the trick to how you use IN OUT parameters in NDS statements.

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-- Enable SERVEROUTPUT.
SET SERVEROUTPUT ON SIZE UNLIMITED
 
-- Declare an anonymous testing block.
DECLARE
 
  -- Declare two local variables.
  lv_super_hero     VARCHAR2(20) := 'Thor';
  lv_super_villain  VARCHAR2(20) := 'Loki';
 
  -- Declare a null statement variable.
  lv_stmt  VARCHAR2(32767);
 
  -- Declare a local procedure to parse the NDS block.
  PROCEDURE print_code_block (pv_block VARCHAR2) IS
    -- Declare local parsing variables.
    lv_length   INTEGER := 1;
    lv_start    INTEGER := 1;
    lv_end      INTEGER := 1;
  BEGIN
    -- Read line by line on a line return character.
    WHILE NOT (lv_end = 0) LOOP
      -- Check for line returns.
      lv_end := INSTR(lv_stmt,CHR(10),lv_start);
      -- Check whether line return has been read.
      IF NOT lv_end = 0 THEN     
        -- Reset the ending substring value and print substring.
        lv_end := INSTR(lv_stmt,CHR(10),lv_start);
        dbms_output.put_line('| '||SUBSTR(lv_stmt,lv_start,lv_end - lv_start));
      ELSE
        -- Print the last substring with a semicolon and exit the loop.      
        dbms_output.put_line('| '||SUBSTR(lv_stmt,lv_start,LENGTH(lv_stmt) - lv_start)||';');
      END IF;
      -- Reset the beginning of the string.
      lv_start := lv_end + 1;      
    END LOOP;    
  END print_code_block;
 
BEGIN
 
  -- Demonstrate good triumps over evil.
  dbms_output.put_line('The good '||lv_super_hero||' beats up the bad '||lv_super_villain||'!');
 
  -- Assign the anonymous block to the local statement variable.
  lv_stmt := 'DECLARE'||CHR(10)
          || '  lv_super_hero     VARCHAR2(20);'||CHR(10)
          || '  lv_super_villain  VARCHAR2(20);'||CHR(10)
          || 'BEGIN'||CHR(10)
          || '  lv_super_hero '||CHR(58)||'= :pv_super_hero;'||CHR(10)
          || '  lv_super_villain '||CHR(58)||'= :pv_super_villain;'||CHR(10)
          || '  :pv_super_hero '||CHR(58)||'= lv_super_villain;'||CHR(10)
          || '  :pv_super_villain '||CHR(58)||'= lv_super_hero;'||CHR(10)
          || 'END;';
 
  -- Run the NDS program.
  EXECUTE IMMEDIATE lv_stmt USING IN OUT lv_super_hero
                                , IN OUT lv_super_villain;
 
  -- Print the diagnostic code block, that's why it used line returns afterall.  
  dbms_output.put_line('--------------------------------------------------');
  print_code_block(lv_stmt);
  dbms_output.put_line('--------------------------------------------------');
 
  -- Demonstrate the world is upside down without Johnny Depp playing Capt'n Jack.
  dbms_output.put_line('The good '||lv_super_hero||' beats up the bad '||lv_super_villain||'!');
 
END;
/

You’ll get the following printed output:

The good Thor beats up the bad Loki!
--------------------------------------------------
| DECLARE
|   lv_super_hero     VARCHAR2(20);
|   lv_super_villain  VARCHAR2(20);
| BEGIN
|   lv_super_hero := :pv_super_hero;
|   lv_super_villain := :pv_super_villain;
|   :pv_super_hero := lv_super_villain;
|   :pv_super_villain := lv_super_hero;
| END;
--------------------------------------------------
The good Loki beats up the bad Thor!

As always, I hope it helps you understand the concept of the USING clause with IN OUT parameters but I hope there’s always better way.

I finally got around to cleaning up old contact me messages. One of the messages raises a question about RESULT_CACHE functions. The writer wanted an example implementing both a standalone schema and package RESULT_CACHE function.

The question references a note from the Oracle Database 11g PL/SQL Programming book (on page 322). More or less, that note points out that at the time of writing a RESULT_CACHE function worked as a standalone function but failed inside a package. When you tried it, you raised the following error message:

PLS-00999: Implementation Restriction (may be temporary)

It’s no longer true in Oracle 11gR2, but it was true in Oracle 11gR1. I actually mentioned in a blog entry 4 years ago.

You can implement a schema RESULT_CACHE function like this:

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CREATE OR REPLACE FUNCTION full_name
( pv_first_name   VARCHAR2
, pv_last_name    VARCHAR2 )
RETURN VARCHAR2 RESULT_CACHE IS
BEGIN  
  RETURN pv_first_name || ' ' || pv_last_name;
END full_name;
/

You would call it like this from a query:

SELECT   full_name(c.first_name, c.last_name)
FROM     contact c;

You can declare a published package RESULT_CACHE function like this:

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CREATE OR REPLACE PACKAGE cached_function IS
  FUNCTION full_name
  ( pv_first_name   VARCHAR2
  , pv_last_name    VARCHAR2 )
  RETURN VARCHAR2 RESULT_CACHE;
END cached_function;
/

You would implement the function in a package body like this:

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CREATE OR REPLACE PACKAGE BODY cached_function IS
  FUNCTION full_name
  ( pv_first_name   VARCHAR2
  , pv_last_name    VARCHAR2 )
  RETURN VARCHAR2 RESULT_CACHE IS
  BEGIN  
    RETURN pv_first_name || ' ' || pv_last_name;
  END full_name; 
END cached_function;
/

You would call the package function like this from a query:

SELECT   cached_function.full_name(c.first_name, c.last_name)
FROM     contact c;

I hope this answers the question.

A question came up today about how to stripe a MySQL view, and this post shows you how. Along with the question, there was a complaint about why you can’t use session variables in a view definition. It’s important to note two things: there’s a workaround and there’s an outstanding request to add lift the feature limitation in Bug 18433.

A striped view lets authorized users see only part of a table, and is how Oracle Database 11g sets up Virtual Private Databases. Oracle provides both schema (or database) level access and fine-grained control access. Fine grained control involves setting a special session variable during a user’s login. This is typically done by checking the rights in an Access Control List (ACL) and using an Oracle built-in package.

You can do more or less the same thing in MySQL by using stored functions. One function would set the session variable and the other would fetch the value for comparison in a view.

Most developers who try this initially meet failure because they try to embed the session variable inside the view, like this trivial example with Hobbits (can’t resist the example with the first installment from Peter Jackson out later this year):

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CREATE VIEW hobbit_v AS
SELECT * FROM hobbit WHERE hobbit_name = @sv_login_name;

The syntax is disallowed, as explained in the MySQL Reference 13.1.20 CREATE VIEW Syntax documentation. The attempt raises the following error message:

ERROR 1351 (HY000): VIEW's SELECT contains a variable or parameter

The fix is quite simple, you write a function that sets the ACL value for the session and another that queries the ACL session value. For the example, I’ve written the SET_LOGIN_NAME and a GET_LOGIN_NAME functions. (If you’re new to stored programs, you can find a 58 page chapter on writing them in my Oracle Database 11g & MySQL 5.6 Developer Handbook or you can use Guy Harrison’s MySQL Stored Procedure Programming.)

You would call the SET_LOGIN_NAME when you connect to the MySQL database as the first thing to implement this type of architecture. You would define the function like the following. (Please note that the example includes all setup statements from the command line and should enable you cutting and pasting it. ;-)):

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-- Change the delimiter to something other than a semicolon.
DELIMITER $$
 
-- Conditionally drop the function.
DROP FUNCTION IF EXISTS set_login_name$$
 
-- Create the function.
CREATE FUNCTION set_login_name(pv_login_name VARCHAR(20)) RETURNS INT UNSIGNED
BEGIN
 
  /* Declare a local variable to verify completion of the task. */
  DECLARE  lv_success_flag  INT UNSIGNED  DEFAULT FALSE;
 
  /* Check whether the input value is something other than a null value. */
  IF pv_login_name IS NOT NULL THEN
 
    /* Set the session variable and enable the success flag. */
    SET @sv_login_name := pv_login_name;
    SET lv_success_flag := TRUE;
 
  END IF;
 
  /* Return the success flag. */
  RETURN lv_success_flag;
END;
$$
 
-- Change the delimiter back to a semicolon.
DELIMITER ;

You can use a query to set and confirm action like this:

SELECT IF(set_login_name('Frodo')=TRUE,'Login Name Set','Login Name Not Set') AS "Login Name Status";

Or, you can use the actual number 1 in lieu of the TRUE, like this:

SELECT IF(set_login_name('Frodo')=1,'Login Name Set','Login Name Not Set') AS "Login Name Status";

Please check this older post on how MySQL manages logical constants and the realities of TRUE and FALSE constants. A more practical example in an API would be this, which returns zero when unset and one when set:

SELECT set_login_name('Frodo') AS "Login Name Status";

The getter function for this example, simply reads the current value of the MySQL session variable. Like the prior example, it’s ready to run too.

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-- Change the delimiter to something other than a semicolon.
DELIMITER $$
 
-- Conditionally drop the function.
DROP FUNCTION IF EXISTS get_login_name$$
 
-- Create the function.
CREATE FUNCTION get_login_name() RETURNS VARCHAR(20)
BEGIN
  /* Return the success flag. */
  RETURN @sv_login_name;
END;
$$
 
-- Change the delimiter back to a semicolon.
DELIMITER ;

Before you test it, lets create a HOBBIT table, seed it with data, and create a HOBBIT_V view. They’re bundled together in the following microscript:

-- Conditionally drop the table.
DROP TABLE IF EXISTS hobbit;
 
-- Create the table.
CREATE TABLE hobbit
( hobbit_id    INT UNSIGNED
, hobbit_name  VARCHAR(20));
 
-- Seed two rows.
INSERT INTO hobbit VALUES ( 1,'Bilbo'),( 1,'Frodo');
 
-- Conditionally drop the view.
DROP VIEW IF EXISTS hobbit_v;
 
-- Create the function-enabled view.
CREATE VIEW hobbit_v AS
SELECT * FROM hobbit WHERE hobbit_name = get_login_name();

A query to the table after setting the session variable will only return one row, the row with Frodo in the HOBBIT_NAME column. It also guarantees an unfiltered UPDATE statement against the view only updates the single row returned, like this:

UPDATE hobbit_v SET hobbit_id = 2;

In a real solution, there are more steps. For example, you’d want your tables in one database, views in another, and functions and procedures in a library database. However, I hope this helps seed some ideas for those interested in creating fine-grained virtual private databases in MySQL with user-authenticated application controls.

Last day of Collaborate 2012 and Scott Spendolini, Sumneva, gave a great presentation on APEX. Only caught the beginning Jan Visser’s Perl presentation because of the distance to the Luxor from the Mandalay South Conference Center and anticipated queuing time for checkout.

We can now look forward to Collaborate 2013 in Denver, Colorado.

Back to observing and working with code, here’s a nice article from MacWorld on how you set up a WebDAV on the Mac. While I’m mentioning Mac OS X and development, there’s still no firm upgrade window for the missing text editing tool – TextMate, and WWDC 2012 tickets sold out in two hours.

Virtualization is important and Dave Welch from the House of Brick gave a great presentation of experiences with VMWare and Tier 1 databases. It was a comprehensive presentation, but the white paper was easier to follow. The slides were complete but the volume of information was a lot for an hour presentation. Well worth the time though.

Utah Oracle User Group (UTOUG) announced a call for Fall Symposium papers today. The Fall Symposium will be in Salt Lake City on 9/6/2012. If you’re interested in presenting on Oracle or MySQL, the call for presentations will be open until 6/15/2012.

The conference party was tonight, and it provided some nice orderves and pizza. The theme was a return to 1980s music, and some folks really dressed their parts. You can listen to a short snapshot of the band by clicking the image to launch a small video segment.

I’m looking forward to the APEX Behind the Scenes presentation at 8:30 a.m. tomorrow. When the conference is over, I won’t miss the smoke filled air that we walk through from the Luxor to the Mandalay. It’s really amazing that the complex is more than a mile in length. It runs from the Luxor to the Mandalay South Conference Center.