boolean.co.nz » MySQL

MySQL datatype for storing IP addresses

Boolean — Fri, 18 May 2012 09:56:24 +0000

The best way to store a (version 4) IP address in a MySQL database is as an integer. This may sound strange but MySQL has two powerful functions to enable you to store an IP address as an unsigned INT. Searching an integer is much faster than searching a string and additionally integers take up less storage space which is great when working with large datasets.

mysql> SELECT INET_ATON(’10.0.5.9′);
———————
INET_ATON(’10.0.5.9′)
———————
167773449
———————
1 row in set (0.00 sec)

and the reverse function

mysql> SELECT INET_NTOA(167773449);
———————
INET_NTOA(167773449)
———————
10.0.5.9
———————
1 row in set (0.00 sec)

MySQL zerofill for numerical types

Boolean — Tue, 06 Mar 2012 19:36:39 +0000

MySQL has a feature for numerical types known as zerofill which effects the display size of numerical types. Unlike string types, the number inside the parentheses is not the storage size in characters for the type. For numerical types the type name itself solely determines storage size.

Column Type	Bytes On Disk	Signed Storage Range	Unsigned Storage Range
tinyint	1 byte	-128 to 127	0 to 255
smallint	2 bytes	-32768 to 32767	0 to 65535
mediumint	3 bytes	-8388608 to 8388607	0 to 16777215
int	4 bytes	-2147483648 to 2147483647	0 to 4294967295
bigint	8 bytes	-9223372036854775808 to 9223372036854775807	0 to 18446744073709551615

So zerofill with default width – the same as int(10):

mysql> create table test_table (t int zerofill);
Query OK, 0 rows affected (0.02 sec)

mysql> insert into test_table set t = 10;
Query OK, 1 row affected (0.02 sec)

mysql> select * from test_table;
+————+
| t |
+————+
| 0000000010 |
+————+
1 row in set (0.08 sec)

And without zerofill:

mysql> create table test_table (t int);
Query OK, 0 rows affected (0.01 sec)

mysql> insert into test_table set t = 10;
Query OK, 1 row affected (0.01 sec)

mysql> select * from test_table;
+——+
| t |
+——+
| 10 |
+——+
1 row in set (0.01 sec)

A common usage for is creating invoice ids such as INV00000945.

Notes:
If you do not have zerofill specified there is no difference between int(3) and int(10)
When doing comparisons: if compared as integers then the values are the same; if you compare as strings the values are different.

MySQL not starting in MAMP OSX

Boolean — Tue, 07 Feb 2012 00:32:03 +0000

Sometimes MySQL doesn’t come up again when attempting to start MAMP, – it just hangs after starting Apache. If you don’t want to have to reboot (and shutting down and restarting MAMP hasn’t helped) then quit MAMP, open a Terminal window and type:

ps aux | grep mysql
lsof -i
killall -9 mysqld

Find the size of all databases on a server

Boolean — Tue, 30 Aug 2011 11:49:33 +0000

A quick way to create a view to show file size statistics across databases on a server.

DROP VIEW IF EXISTS alldb;
CREATE VIEW AllDatabases AS
SELECT
s.schema_name AS ‘Schema’,
SUM (t.data_length) AS Data,
SUM ( t.index_length ) AS Indexes,
SUM (t.data_length) + SUM (t.index_length) AS ‘Mb Used’,
IF (SUM(t.data_free)=0,”,SUM (t.data_free)) As ‘Mb Free’,
IF (SUM(t.data_free)=0,”, 100 * (SUM (t.data_length) + SUM (t.index_length)) / ((SUM (t.data_length)+SUM (t.index_length) + SUM (IFNULL(t.data_free,0))) ) ) AS ‘Pct Used’, COUNT (table_name) AS Tables
FROM information_schema.schemata s
LEFT JOIN information_schema.tables t ON s.schema_name = t.table_schema
GROUP BY s.schema_name
WITH ROLLUP

Exporting a MySQL Database Schema as XML

Boolean — Fri, 26 Mar 2010 10:10:12 +0000

Dumping a database schema is a an often required quick task. This script will read the schema from a MySQL database, and output it XML to describe it.

// Define a few constants
define(“DB_SERVER”, “localhost”);
define(“DB_USER”, “root”);
define(“DB_PASS”, “password”);
define(“DB_NAME”, “example”);

// Lets connect to the db
$dbhandle = mysql_connect(DB_SERVER, DB_USER, DB_PASS)
or die(“Unable to connect to MySQL”);

// Choose a database to work with
$selected = mysql_select_db(DB_NAME, $dbhandle)
or die(“Could not select examples”);
// Return all of the available tables
$result_tbl = mysql_query( “SHOW TABLES FROM “.DB_NAME, $dbhandle );

$tables = array();
while ($row = mysql_fetch_row($result_tbl)) {
$tables[] = $row[0];
}

$output = “\n”;
$output .= “”;

// Now iterate through each table and return the fields
foreach ( $tables as $table ) {
$output .= “

”;
$result_fld = mysql_query( “SHOW FIELDS FROM “.$table, $dbhandle );

while( $row1 = mysql_fetch_row($result_fld) ) {
$output .= “ $output .= ($row1[3] == “PRI”) ? ” primary_key=\”yes\” />” : ” />”;
}

$output .= “

”;
}

$output .= “”;

// Notify the browser the type of file being dealt with
header(“Content-type: text/xml”);
// Display the XML to describe the schema
echo $output;

// Dont forget to close the connection
mysql_close($dbhandle);
?>

Remember, this is an example, and real world code should escape characters, follow best security practices etc. Proof of concept code here, – not a snippet to put live.

Scheduling mySQL backups

Boolean — Fri, 19 Feb 2010 02:31:55 +0000

I’m sure there is no need to explain the virtues of regular backups. Below are three steps to peace of mind

1) Configure a backup directory on the server

mkdir /var/lib/backupfolder
cd /var/lib/backupfolder

2) Make a backup script

vi mysqlbackup.sh

#!/bin/sh
# MySQL server username goes here
USERNAME=”username”
# MySQL server password goes here
PASSWORD=”password”
# List of DBNAMES for Backup
DBNAME=”dbname”
#date timestamp used in the log
DATE=`/bin/date +%Y-%m-%d_%Hh%Mm`
# format the output file
OUTDIR=”/var/lib/backupfolder/”
OUTFILE=”ip_bindass”.$DATE.”sql.gz”
#working directory
DIR=”/var/lib/backupfolder/”
#cd $DIR
# Do the MySQL Backup
/usr/bin/mysqldump –database $DBNAME –opt –single-transaction -u$USERNAME -p$PASSWORD | /usr/bin/gzip -9 > $OUTDIR$OUTFILE

Dont forget to change permissions

chmod +x mysqlbackup.sh

3) Schedule the backup in crontab

crontab -e

Add something along the lines of:

30 23 * * * /var/lib/backupfolder/mysqlbackup.sh

To backup at 11:30PM every day. Just as important as to backup up is to test restores; – it’s no good having backups and feeling at ease if you cant recover in the event of catastrophe!

Help keep the internet free

Boolean — Fri, 01 Jan 2010 21:44:48 +0000

A big part of the Internet is built on LAMP (Linux, Apache, MySQL and PHP/Perl/Python). Now Oracle is trying to buy Sun, which owns MySQL.

It’s not in the Internet users interest that one key piece of the net would be owned by an entity that has more to gain by severely limiting and in the long run even killing it as an open source product than by keeping it alive. If Oracle were allowed to acquire MySQL, we would be looking at less competition among databases, which will mean higher license and support prices. In the end it’s always the consumers and the small businesses that have to pay the bills, in this case to Oracle.

Read on here at Monty’s blog (creator of MySQL) or head here for the official website.

Using LIMIT when querying a single row

Boolean — Fri, 27 Nov 2009 13:49:07 +0000

Sometimes you know you are only looking for one row when you are querying your tables. It may be that you are fetching a unique record or checking the existence of any number of records that satisfy your WHERE clause.

Adding LIMIT 1 to your query can increase performance in this situation; – the database engine will stop scanning for records after it finds just one, instead of going through the whole table or index.

For example:

$record = mysql_query(“SELECT username FROM user WHERE country = ‘UK’”);
if (mysql_num_rows($record) > 0) {
// …
}

Can become:

$record = mysql_query(“SELECT username FROM user WHERE country = ‘UK’ LIMIT 1″);
if (mysql_num_rows($record) > 0) {
// …
}

Maxlength for MySQL TEXT field types

Boolean — Fri, 08 May 2009 08:33:56 +0000

MySQL supports four TEXT field types (TINYTEXT, TEXT, MEDIUMTEXT and LONGTEXT)

MyISAM tables in MySQL have a maximum row size 65,535 bytes and all the data in a row must fit within that limit.

Luckily however TEXT field types are stored outside of the table itself and thus only contribute 9 – 12 bytes towards that limit.

MySQL date_format

Boolean — Tue, 21 Apr 2009 16:48:56 +0000

I always seem to be digging around to find MySQL’s date formatting syntax, so here is a couple of common conversions…

select date_format(date, ‘%d %M %Y’) as new_date from tablename

where date is the name of your date field, and new_date is the variable name which you can use to reference the value.

date_format String	Example
‘%e/%c/%Y’	25/4/2009
‘%c/%e/%Y’	4/25/2009
‘%d/%m/%Y’	25/04/2009
‘%m/%d/%Y’	04/25/2009
‘%a %D %b %Y’	Fri 25th Apr 2009

A more complete list of specifiers is available here.