You have an error in your SQL syntax; check the manual that corresponds
to your MySQL server version for the right syntax to use near 'USING
BTREE, KEY `index` (`fields`)' at line 1

It worked fine before, so why won’t ant create this table?

Well its down to the USING BTREE on MySQL Server version 5.0 using a InnoDB or MyISAM table. You can only have BTREE as an index and thus any reference to it on 5.0 seems to fail. May as well just take out the reference to the index type.

Annoying if you can’t work out the error, but now you know.

CREATE TABLE inventory(
    inventory_id INT AUTO_INCREMENT,
    discriminator_column VARCHAR(20),
    category VARCHAR(50) NOT NULL,
    part_number VARCHAR(50) NOT NULL,
    PRIMARY KEY (inventory_id),
    KEY category_part_number (category, part_number),
    KEY discriminator_column (discriminator_column)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE inventory_room(
    inventory_id INT NOT NULL,
    rack_limit INT(6),
    room_type VARCHAR(25),
    KEY inventory_id (inventory_id),
    CONSTRAINT inventory_room_key FOREIGN KEY (inventory_id) REFERENCES inventory (inventory_id)
        ON DELETE CASCADE
        ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

You have to have a discriminator field so that Doctrine can connect the tables nicely when its joining them.

<?php
namespace Net\Model\Inventory;
use Doctrine\ORM\Mapping as ORM;

/**
 * Inventory entity
 *
 * @ORM\Entity(repositoryClass="Net\Repository\Inventory")
 * @ORM\Table(name="inventory")
 * @ORM\InheritanceType("JOINED")
 * @ORM\DiscriminatorColumn(name="discriminator_column", type="string")
 * @ORM\DiscriminatorMap({"inventory" = "AbstractItem", "inventory_room" = "Room"})
 *
 * @category Net
 * @package  Model
 */
abstract class AbstractItem
{
    /**
     * @ORM\Id @ORM\Column(name="inventory_id") @ORM\GeneratedValue
     * @var int
     */
    protected $inventory_id;

    /**
     * @ORM\Column(type="string")
     * @var string
     */
    protected $category;    

    /**
     * @ORM\Column(type="string")
     * @var string
     */
    protected $part_number;
 }

As you can see in the above class, we have a ORM\GeneratedValue field. This tells Doctrine that this field is an increment field. As this is a one-to-one relationship we do not need one in the inventory_room table as it will be joined on the inventory_id field.

In the next class, this is the child class that extends the abstract. So Doctrine will read the annotations at the top and see that its a joined table using the id field (inventory_id)

<?php
namespace Net\Model\Inventory;
use Doctrine\ORM\Mapping as ORM;

/**
 * Inventory Room entity
 * @ORM\Entity
 * @ORM\Table(name="inventory_room")
 *
 * @category Net
 * @package  Model
 */
class Room extends AbstractItem
{
    /**
     * @ORM\Column(type="string")
     * @var string
     */
    protected $room_type;

    /**
     * @ORM\Column(type="string")
     * @var string
     */
    protected $rack_limit;
}

Anyway, to reset a password, you need to stop MySQL and restart it with a special setting that allows you to login without passwords. Obviously this is a dangerous switch and you have to remember to stop and start MySQL after you’ve finished!

Linux:

Login with superuser access (sudo su)

> /etc/init.d/mysql stop

This will stop the MySQL service on the server, and all connections will be cut off.

Then we need to start MySQL with the secret switch:

> mysqld_safe --skip-grant-tables &

I don’t get any messages after this, but you may get one saying the mysqld_safe has started.

Then connect as root:

> mysql -u root

You will be connected. And you can just assign the root user a new password:

mysql> USE mysql;
mysql> UPDATE user SET password=PASSWORD(NEWPASSWORD) WHERE user = "root";
mysql> FLUSH PRIVILEGES;
mysql> exit;

That’s it. So now, just stop and start mysql again (as superuser) and were done:

> /etc/init.d/mysql restart

> mysqladmin -u root password NEWPASSWORD

This will assign the root user, the password in NEWPASSWORD

But, what if you want to change the root’s password?

> mysqladmin -u root -pOLDPASSWORD password NEWPASSWORD

i.e.

> mysqladmin -u root -pabcdefg password gfedcba

The above example will change the root’s password (if it is right) from abcdefg to gfedcba (I know this isn’t a very strong password, but its only an example)

You can of course, log into MySQL to change the password for any user by following these commands:

> mysql -u root -pADMINPASSWORD

mysql> USE mysql;
mysql> UPDATE user SET password=PASSWORD('NEWPASSWORD') WHERE user = "root";
mysql> FLUSH PRIVILEGES;

Done.

If you forget your root password, then see my post on forgotten MySQL root password…

SET profiling = 1;

This will turn on the profiling. Then for each query you run, MySQL will log all the queries and extra information about them.

Run yourself some queries, and then run this command:

SHOW PROFILES;

It will show you a standard MySQL recordset of the queries you have run, each with an individual ID, in the order that you ran them.

+----------+-------------+--------------------------------------------------------+
| Query_ID | Duration    | Query                                                  |
+----------+-------------+--------------------------------------------------------+
|        1 |  0.00009260 | SELECT fieldname FROM table WHERE field = 'value'      |
+----------+-------------+--------------------------------------------------------+

SHOW PROFILE FOR QUERY 1;

+--------------------------------+----------+
| Status                         | Duration |
+--------------------------------+----------+
| starting                       | 0.000033 |
| checking query cache for query | 0.000073 |
| Opening tables                 | 0.000013 |
| System lock                    | 0.000007 |
| Table lock                     | 0.000035 |
| init                           | 0.000032 |
| optimizing                     | 0.000014 |
| statistics                     | 0.000016 |
| preparing                      | 0.000014 |
| executing                      | 0.000009 |
| Sending data                   | 0.331296 |
| end                            | 0.000016 |
| end                            | 0.000003 |
| query end                      | 0.000005 |
| storing result in query cache  | 0.000105 |
| freeing items                  | 0.000012 |
| closing tables                 | 0.000007 |
| logging slow query             | 0.000003 |
| logging slow query             | 0.000048 |
| cleaning up                    | 0.000006 |
+--------------------------------+----------+
20 rows in set (0.00 sec)

SHOW PROFILE CPU FOR QUERY 1;

If you want to make a super quick backup of a MySQL database, the best tool for the job is the native mysqldump. Its also a command line utility, so you can use it from a telnet or SSH connection, etc…

The basic command structure of mysqldump is:

mysqldump -u {username} -p{password} {database} > {backup-file}

I.e. If you had root access, and you wanted to backup all the tables within the “customers” database you could run this command:

mysqldump -u root -p customers > mybackup.sql

This would dump all the data to the mybackup.sql file. Note I didn’t enter a password. Mysql will ask you for your password in this instance. If you wanted to enter the password (where it could be seen, or saved into a BASH history) then you use the command -pABC123 where ABC123 is the password (not the lack of a space between -p and ABC123 – this is important!)

But if you are security conscious, omit the actual password from the command line, and merely use -p as this will prompt you for the password and therefore BASH or DOS will not store it.

If you wanted to only dump certain tables from the database, specify them after the database. For example, to back up the “address” and “billing” tables:

mysqldump -u root -p customers address billing > mybackup.sql

Restoring a mysqldump file

If you want to restore a mysqldump’ed file into MySQL – you can simply run the following command:

mysql -u {username} -p{password} {database} < {backup-file}

Note the change of direction for the < symbol and the fact we’re calling the mysql command, and not the mysqldump command!!!

So, to squirt my backupfile back into the customers database

mysql -u root -pABC123 customers < mybackup.sql

NB. This will overwrite your current database tables with whatever is in the backupfile!

Using mysqldump to backup ALL databases

If you have lots of databases, then you simply use the –all-databases command to back them all up into one file:

mysqldump -u root -pABC123 --all-databases > mytotalbackup.sql

Using mysqldump to backup multiple databases

By using the –databases switch, we can state which databases we want backed up. Separate each database name with a space.

So to backup “customers”, “orders” and “misc” we use the following syntax:

mysqldump -u root -pABC123 --databases customers orders misc > multiple-databases.sql

Advanced techniques

Compressed backups

More often than not, a database dump will be several hundred MB in size, if not more. MySQL can zip this for you automatically using the gzip command:

mysqldump -u root -pABC123 customers | gzip > compressed-backup.sql.gz

The pipe before the gzip tells mysqldump to send the output to the next command, which is gzip and that, in turn, is asked to create “compressed-backup.sql.gz”

Dumping the data definitions

If you wanted a “skeleton” structure of the entire database, then mysqldump will allow this, by using the –no-data switch:

mysql -u root -pABC123 --no-data customers > customers-structure.sql

If you know a time span that you need to investigate, then you can easily use the mysqlbinlog utility:

mysqlbinlog --start-datetime="2010-07-27 14:30:00" --stop-datetime="2010-07-27 15:00:00" > backup.txt

This will export all the recorded SQL Statements performed between 2:30pm and 3pm on the 27th July 2010 to the text file “backup.txt”. I can then browse at my convenience.

If you need to re-create any of the statements, you can copy and paste into your MySQL client of choice.

SELECT country, population,
CASE country
WHEN 'United Kingdom' THEN 0
WHEN 'United States' THEN 1
WHEN 'New Zealand" THEN 2
ELSE country
END AS countrySort
FROM countryList 
ORDER BY countrySort ASC;

This will sort the results by country, but with UK, US, NZ as the top three.

We use ANT for releasing versions of our PHP applications. Its very smart and takes a lot of the problems related to releases out of the equation.

However, everytime we performed a release, our replication server would break, and I’d have to skip a load of database delta error messages with this command:

SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1

The error we received is:

Error 'Incorrect string value: 'x9CxF37x12[k...' for
column 'applied_by' at row 1' on query. Default database:
'<databasename>'.

Query: 'INSERT INTO changelog (change_number, delta_set, complete_dt,
applied_by, description)

VALUES (35, 'Main', CURRENT_TIMESTAMP, USER(),
'<database_delta_filename>')'.

I’d been getting these errors for a while.

Basically, the MySQL server was replicating the changelog table down to the slave, but for some reason it just would not accept the replicated query.

After a bit of scrummaging around, and changing field values/character sets, I discovered that in the string was “x80″ which is a padding character as set out in http://en.wikipedia.org/wiki/ISO_8859-1 and shouldn’t be used in a string. I’m not really sure how it got there, or why, but I basically changed the “applied_by” field to be a BLOB – which is generically a VARCHAR with no character set and there fore ignores this.

Unbelievable that I’d not found this function before…

SELECT REPLACE(fieldname, "look for", "replace with") FROM tablename;

So simple…