#1005 – Can’t create table
Full error message: #1005 – Can’t create table ‘.\my_db\#sql-7c4_444.frm’.
Using MySQL version 4.1.22-community-nt, I created two tables (`table1` and `table2`) in a database (let’s call it `my_db`) as follows:
CREATE TABLE `table1` ( `idtable1` int(10) unsigned NOT NULL auto_increment, `table1_str` varchar(50) NOT NULL default '', PRIMARY KEY (`idtable1`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE `table2` ( `idtable2` int(10) unsigned NOT NULL auto_increment, `idtable1_fk` int(10) NOT NULL, `table2_str` varchar(50) NOT NULL default '', PRIMARY KEY (`idtable2`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Then I tried to add a foreign key constraint like this:
ALTER TABLE `table2` ADD CONSTRAINT `table2_ibfk_1` FOREIGN KEY (`idtable1_fk`) REFERENCES `table1` (`idtable1`) ON DELETE CASCADE ON UPDATE CASCADE;
And then I got the error.
The solution in my case was adding the unsigned attribute to the `idtable1_fk` field in `table2` for having the same type as the field `idtable1` it references in `table1`:
ALTER TABLE `table2` CHANGE `idtable1_fk` `idtable1_fk` int(10) unsigned NOT NULL;
After that I ran the foreign key constraint query:
ALTER TABLE `table2` ADD CONSTRAINT `table2_ibfk_1` FOREIGN KEY (`idtable1_fk`) REFERENCES `table1` (`idtable1`) ON DELETE CASCADE ON UPDATE CASCADE;
And then it worked. But if you don’t have the same problem but you get the same error message you might already have a foreign key constraint with the given name. For example, if I run again the foreign key constraint query I will get the same error. Be careful if you use phpMyAdmin as a visual interface for MySQL, because it seems to me that it does not show us all the foreign key constraints we added to a table. If you want to see which foreign key constraints a table has, you could export the structure of that table and analyze the foreign key constraints queri(es).
Hope this works for you, too.
Conclusion: We should make sure that the possible values of the foreign key field are in the same range as the possible values of the field referenced by that foreign key and that there is no foreign key constraint with the same name as the constraint we are trying to add.
How to uninstall Google Toolbar for Firefox
Problem: Because I did not use Google Toolbar (it was automatically installed when I installed Firefox), I decided to uninstall it. I selected the Uninstall option in Tools -> Add-ons -> Google Toolbar in Firefox (Disable option being grayed) and it said that the toolbar will be uninstalled the next time Firefox will restart. So I closed and started Firefox again and I got a popop window that said something like thanks for installing Google Toolbar and if I want to see the page rank for every site I visit etc. This window kept appearing until I agreed installing Google Toolbar. I also tried uninstalling the toolbar using its uninstall setting, but I kept getting the same (reversed) result.
Everytime I closed the Firefox browser window I got sure that the procees was closed (no instances of FF remained opened).
My operating system is Windows XP Professional.
The solution that worked for me consists of two simple steps:
1. I uninstalled Google Toolbar for Internet Explorer using Control Panel -> Add/Remove programs.
2. I pressed Disable (not grayed anymore) and then Uninstall buttons for Google Toolbar in Firefox Tools -> Add-ons and restarted Firefox.
And it worked! No annoying popop window anymore.
1144: Interface method set data in namespace is implemented with an incompatible signature in class .
Full error message: 1144: Interface method set data in namespace is implemented with an incompatible signature in class.
<package:class><mypackage:myclass></mypackage:myclass></package:class>
This error appears in Flex Builder / Eclipse on the Problems Tab.This error refers to the fact that an extended class named <package.class> with an over ridable function has a correspondent override in <mypackage:myclass> that doesn’t match the overrided function. To be more specific i’ll give you an example:
Let’s say we want to create a custom data grid header renderer and in order to do this we will create a class VerticalHeaderRenderer that will extend DataGridItemRenderer. In the class VerticalHeaderRenderer we will override the setter function for the data property like this:
override public function set data(value:Object):void{
local_var = value.toString();
}
This is the correct version and it will not give the error mentioned in the title but if we have a function that has a parameter of a different type then Object or a different return type we will receive the error.
Basically this error tells us that we are trying to override a function with different parameters or different return value type. So to escape this error you must ensure that the override is made correctly.
Hope this helps.
Good luck.
How to use specific language characters with PHP and MySQL (example: Romanian)
Problem: Using specific characters from European languages like Romanian, Bulgarian, Czech and so on (usually the ones without support in ISO 8859-1) rises errors when displaying the content in browsers turning special characters in unrecognizable ones.
My fix for this problem is using UTF-8 character set encoding for every page of the website and the MySQL tables that contain the fields you are using. Also all the html encodings from PHP use the UTF-8 character set encoding (this is not mandatory).
If you already have the database, but with the default character set (latin1) and collation (latin1_swedish_ci) for the tables with text fields (of type CHAR, VARCHAR, TEXT etc) in which you need to have special characters, you should change the character set of each of those tables like this:
ALTER TABLE my_table CONVERT TO CHARACTER SET utf8;
If you don’t have the database then you should create it and when you create a table that you need to use with specific language characters, you should specify the character set for that table:
CREATE TABLE `my_table` ( `idmy_table` tinyint(3) unsigned NOT NULL auto_increment, `my_field` varchar(255) NOT NULL default '', PRIMARY KEY (`idmy_table`) ) CHARSET=utf8;
The most important thing is that in PHP, after opening a database connection, before executing any query to the database, you should ensure that this code is executed
mysql_query("SET NAMES utf8", $my_conn);
This tells the server what character set the client is using for sending SQL statements and the character set the server should use to return the results to the client.
A simple example:
<?php
$my_conn = @mysql_connect("localhost", "user", "pass")
or die("There was a problem connecting to MySQL. Please try again later.");
if(!@mysql_select_db("test", $my_conn))
{
die ("There was a problem connecting to the database. Please try again later.");
}
mysql_query("SET NAMES utf8", $my_conn);
if(!empty($_GET['mystr']))
{
// insert the string into the database
$str = htmlspecialchars($_GET['mystr'], ENT_QUOTES, "UTF-8");
$query = "INSERT INTO my_table_t (my_field) VALUES('".$str."')";
$result = mysql_query($query, $my_conn);
if($result)
{
// save the id of the table row inserted
$last_insert_id = mysql_insert_id($my_conn);
// get the last inserted value
$query = "SELECT my_field FROM my_table_t WHERE idmy_table = '".$last_insert_id."'";
$result = mysql_query($query, $my_conn);
if($result && $row = mysql_fetch_array($result, MYSQL_ASSOC))
{
$db_string = $row['my_field'] ;
}
}
}
elseif(!empty($_GET['searchstr']))
{
$str = htmlspecialchars($_GET['searchstr'], ENT_QUOTES, "UTF-8");
$query = "SELECT * FROM my_table_t WHERE my_field LIKE '%".$str."%'";
$result = mysql_query($query, $my_conn);
if($result)
{
while($row = mysql_fetch_array($result, MYSQL_ASSOC))
{
$search_results[$row['idmy_table']] = $row['my_field'];
}
}
}
mysql_close($my_conn);
?>
<html>
<head>
<title>Page title</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head>
<body>
<?php
if(!empty($db_string))
{
echo "<strong>Inserted string</strong>: $db_string<br />";
}
?>
<form method="get" action="">
String to insert into the database <input type="text" name="mystr"/>
<input type="submit" value="GO"/>
</form>
<?php
if(!empty($search_results))
{
echo "<strong>Search results</strong>:<br />";
foreach($search_results as $id => $value)
{
echo $value."<br />";
}
}
?>
<form method="get" action="">
Search query <input type="text" name="searchstr"/>
<input type="submit" value="GO"/>
</form>
</body>
</html>
Tip: The search in Romanian language over the database (tested with MySQL LIKE operator) works like a charm when searching words that have special characters or not.
For example: In Romanian language the word “peasant” is written as “ţăran” and someone who searches it gets the same result for the search terms “taran” or “ţăran” or “ţaran” or “tărân” and so on – so this is the real magic.
UPDATE: You may also need to add a header to the php script if you use ob_start or similar php functions like this:
header("Content-type: text/html; charset=UTF-8");
this usually fixes the encoding selection in Internet Explorer for this case.
Problem: When submitting a form, seems like another form gets submitted
Actually, I had two forms on the same page, one with the GET method (let’s call it get_form), the other with the POST method (we’ll call it post_form). When I pressed the submit button of get_form it seemed that the post_form got submitted. In fact, all the variables in get_form and post_form were passed with the POST method.
So the natural thing that came into my mind was that the two forms were intersecting. But how? I knew for sure they were separate forms because get_form was in a file that I was including in the file that contained post_form, after post_form.
After verifying the HTML source over and over again I finally solved the mistery. There was a stupid mistake I made: I did not close post_form properly. Instead of using the form closing tag </form> at the end of post_form, i put the form opening tag <form> and every time I checked for the problem, I missed an important detail: the lack of the slash sign.
Conclusion: When opening a HTML element, make sure to close it accordingly.
How to receive a failure notice when the recipient cannot be reached after sending an email using the PHP mail() function
I could not receive a failure notice when sending email to an email address that does not exist ($to_address), using this code:
$subject = "Email subject"; $message = "line1\r\nline2\r\nline3"; $headers = "MIME-Version: 1.0\r\n"; $headers .= "Content-type: text/plain; charset=iso-8859-1\r\n"; $headers .= "To: <$to_email>\r\n"; $headers .= "From: Me <$my_email_address>\r\n"; $headers .= "Return-Path: <$my_return_email_address>r\n"; mail($to_email, $subject, $message, $headers);
The problem was that the email address I wanted to receive the failure notices to ($my_return_email_address) was not the same as the value of the configuration option sendmail_from in the php.ini file (Apache web server installed on a machine with the Windows Professional operating system). So the failure notices were sent to the sendmail_from email address if this was an existing address, instead of the email address specified in the Return-path header of the email.
The solution is replacing the lines:
$headers .= "Return-Path: <$my_return_email_address>r\n"; mail($to_email, $subject, $message, $headers);
with:
// when the PHP server runs on Windows ini_set(sendmail_from, $my_return_email_address); mail($to_email, $subject, $message, $headers); ini_restore(sendmail_from);
// when the PHP server runs on UNIX mail($to_email, addslashes($subject), $message, $headers, "-r $my_return_email_address");
This means that, before sending the email, we set the value of the sendmail_from configuration option to $my_return_email_address and we restore the default value of the configuration option after the email is sent.
How to check/uncheck a bunch of checkboxes without using ids for the checkbox inputs
My solution of checking/unchecking a group of HTML checkboxes using Javascript implies using an array of checkboxes, which means naming all the inputs of type ‘checkbox’ like array_name[]. Example:
<form name="cb_form"> <input type="checkbox" name="cb[]" value="0" />Zero <input type="checkbox" name="cb[]" value="1" />One <input type="checkbox" name="cb[]" value="2" />Two <input type="checkbox" name="cb[]" value="3" />Three </form>
In this example, the name of the checkboxes array is cb.
Next, we place two links for checking/unchecking all checkboxes in our array. If someone clicks one of these links, the checkAll() JavaScript function is called:
<a href="" onclick="checkAll('cb_form', 'cb[]', true); return false;">Check all<a>
<a href="" onclick="checkAll('cb_form', 'cb[]', false); return false;">Uncheck all<a>
The checking/unchecking all checkboxes function in JavaScipt looks like this:
function checkAll(form_name, cb_name, value)
{
var cb_arr = document.forms[form_name].elements[cb_name];
// if the checkboxes exist
if(cb_arr)
{
// if the number of checkboxes is at least 2
if(cb_arr.length > 1)
{
// for each checkbox
for(i = 0; i < cb_arr.length; i++)
{
// check (value == true) or uncheck (value == false) it
cb_arr[i].checked = value;
}
}
else // cb_arr.length is undefined which means there is a single checkbox element that is not considered an array of one element
{
cb_arr.checked = value;
}
}
}
Note that if we only have one checkbox, the variable cb it is not considered an array, but a normal variable. This is useful in the situation of dinamically generated HTML pages (using PHP, for example) and the number of checkboxes varies from page to page.
You can test the example here:
Warning: mail(): SMTP server response: 451 See http://pobox.com/~djb/docs/smtplf.html. in path_to_php_file on line #
Full error message: Warning: mail(): SMTP server response: 451 See http://pobox.com/~djb/docs/smtplf.html. in path_to_php_file on line #
This is an error message that I got lots of times and it was always the same problem. So I decided to write here the solution for the next time I encounter it and I thought it might also help other people.
So I tried to send an email in plain text using the PHP function mail() :
// consider this being an existing email address $to_address = "abc@def.com"; $subject = "Email subject"; $message = "line1 line2 line3"; $headers = "MIME-Version: 1.0\r\n"; $headers .= "Content-type: text/plain; charset=iso-8859-1\r\n"; $headers .= "To: <".$to_email.">\r\n"; $headers .= "From: Me <".$my_email_address.">\r\n"; mail($to_email, $subject, $message, $headers);
It worked fine with Apache server running on Linux operating system, but I got the error message mentioned before with the server running on Windows.
It looks like while Unix-based systems recognize \n character (the equivalent in PHP of LF – line feed) as a newline even when sending emails, Windows systems are stricter in comunicating using some textual Internet Protocols (such as SMTP) that mandate the line terminator to be the ASCII CR+LF (carriage return + line feed) sequence, which is abstracted in PHP to \r\n character sequence.
So the problem was the $message variable. The correct way to assign the multiple lines value to it is:
$message = "line1\r\nline2\r\nline3"; // separate the lines with \r\n // or, elegantly: $message = "line1\r\n"; $message .= "line2\r\n"; $message .= "line3";
And now it works on Windows, too.
warning C4244: ‘argument’ : conversion from ‘double’ to ‘int’, possible loss of data
Full error message: warning C4244: ‘argument’ : conversion from ‘double’ to ‘int’, possible loss of data
Error occured on Visual Studio 2003 when compiling a C++ project.
The warning occurred because i was calling the abs function and i did not have included yet the math.h file. The reason that this warning appeared was due to the abs function that was already loaded with other libraries (stdlib.h) and it had only one defined as int abs(int) but I needed the double abs(double) overload. This way the compiler needed to let me know about the implicit cast from double to int.
Example:
double y = 1.2454; double x = abs((double)y);
Fix:
#include <math.h>
The fix in my case is the following code added to the header of the file #include <math.h>
org.hibernate.HibernateException: identifier of an instance of members.Appointment was altered from 8 to 8
Full error message:
Exception occurred during event dispatching: org.hibernate.HibernateException: identifier of an instance of members.Appointment was altered from 8 to 8 at org.hibernate.event.def.DefaultFlushEntityEventListener.checkId(DefaultFlushEntityEventListener.java:58) at org.hibernate.event.def.DefaultFlushEntityEventListener.getValues(DefaultFlushEntityEventListener.java:157) at org.hibernate.event.def.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:113) at org.hibernate.event.def.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:196) at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:76) at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:26) at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1000) at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:338) at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:106) at members.AppointmentDialog.jButtonSaveActionPerformed(AppointmentDialog.java:279) at members.AppointmentDialog.access$000(AppointmentDialog.java:21) at members.AppointmentDialog$1.actionPerformed(AppointmentDialog.java:101) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1849) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2169) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236) at java.awt.Component.processMouseEvent(Component.java:5517) at javax.swing.JComponent.processMouseEvent(JComponent.java:3135) at java.awt.Component.processEvent(Component.java:5282) at java.awt.Container.processEvent(Container.java:1966) at java.awt.Component.dispatchEventImpl(Component.java:3984) at java.awt.Container.dispatchEventImpl(Container.java:2024) at java.awt.Component.dispatchEvent(Component.java:3819) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3892) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822) at java.awt.Container.dispatchEventImpl(Container.java:2010) at java.awt.Window.dispatchEventImpl(Window.java:1791) at java.awt.Component.dispatchEvent(Component.java:3819) at java.awt.EventQueue.dispatchEvent(EventQueue.java:463) at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:153) at java.awt.Dialog$1.run(Dialog.java:535) at java.awt.Dialog$2.run(Dialog.java:563) at java.security.AccessController.doPrivileged(Native Method) at java.awt.Dialog.show(Dialog.java:561) at java.awt.Component.show(Component.java:1302) at java.awt.Component.setVisible(Component.java:1255) at admin.AdminOptionsForm.jButtonSetAppointmentActionPerformed(AdminOptionsForm.java:238) at admin.AdminOptionsForm.access$800(AdminOptionsForm.java:24) at admin.AdminOptionsForm$9.actionPerformed(AdminOptionsForm.java:145) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1849) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2169) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236) at java.awt.Component.processMouseEvent(Component.java:5517) at javax.swing.JComponent.processMouseEvent(JComponent.java:3135) at java.awt.Component.processEvent(Component.java:5282) at java.awt.Container.processEvent(Container.java:1966) at java.awt.Component.dispatchEventImpl(Component.java:3984) at java.awt.Container.dispatchEventImpl(Container.java:2024) at java.awt.Component.dispatchEvent(Component.java:3819) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3892) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822) at java.awt.Container.dispatchEventImpl(Container.java:2010) at java.awt.Window.dispatchEventImpl(Window.java:1791) at java.awt.Component.dispatchEvent(Component.java:3819) at java.awt.EventQueue.dispatchEvent(EventQueue.java:463) at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149) at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
In Java, I had a class Appointment mapped to a MySQL table `appointment` using Hibernate as follows:
<hibernate-mapping> <class name="members.Appointment" table="appointment"> <id name="idAppointment" column="idappointment" type="short"> <generator class="native"/> </id> <many-to-one name="member" column="idmember" not-null="true" foreign-key="fk_idmember"/> <property name="startDate" type="timestamp" column="start_date"/> <property name="duration" type="short" column="duration" length="3"/> <property name="cancelled" type="boolean"/> </class> </hibernate-mapping>
I was getting the error when inserting a new appointment into the database.
The problem was that the idAppointment member variable in the Java class and the idappointment field in the MySQL database table were of the type int. So why the hell did I have the type short in the mapping? The answer is simple: because of the copy paste. So the correct code is:
<id name="idAppointment" column="idappointment"> <generator class="native"/> </id>
Conclusion: copy paste is sometimes evil.
