1. Make sure your username and password are correct.
2. Double-check the hostname. Although “localhost” works on most servers, it may not on yours.
3. Test the connection string (if you wrote the code yourself). You may have a simple typo.
4. If you have your own server, check the mysql server to see if it is running and running without errors.
5. Does the database you are trying to connect to actually exist? Sometimes automatic database creation fails, and you are left wondering why you cannot connect to it.
6. If you can connect locally but cannot connect remotely, check your firewall settings to see if port 3306 (or whichever port you use for mysql) is open.
7. Finally, be sure your mysql user has the necessary privileges to perform whatever task you are trying to accomplish.

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To search MySQL from the command line, you need to log in to MySQL and perform a query.

Login as root:

mysql -u root -p
You should get a prompt like “mysql>”

To do a basic search, use the SELECT command. For example, to search for all records with the title of “Sales” that also have the number “44”, enter:

mysql> SELECT * FROM [table name] WHERE title = "Sales" AND number = '44';

You can perform similar queries on any tables in your database. For a more in-depth guide to queries, consult the MySQL documentation.

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query_cache_limit=1M
query_cache_size=32M (32MB for every 1GB of RAM)
query_cache_type=1

2. Key buffer size – This refers to the size of buffers used for indexes. A larger buffer will result in faster SQL response time when a command is issued. The key_buffer_size should be at least 1/4 but no more than 1/2 of the RAM size of the server.

key_buffer=256M (128MB for every 1GB of RAM)

3. Table cache – Just like MySQL can cache queries, it can also cache tables. If you think about how often a database table would be accessed, especially when using content management systems and web applications, this only makes sense. You can adjust this according to your memory.

table_cache=1500

Next week, we will cover more MySQL optimization tips.

Source: linuxstuffs

You can accomplish basic optimization of database tables from within your web-based control panel or in phpMyAdmin. You should do this routinely. But there are also ways you can optimize the server itself to serve databases faster and more securely. Over the remainder of this week, I will show you a few tips to optimize your MySQL server. Today, I will just point you to the right file.

To begin configuring your MySQL server, you will need to locate the configuration file. This will differ, depending on your operating system and even from one Linux distribution to another. Most commonly, it will be in a directory like /etc/mysql, and the file will be called my.cnf. You will need to edit it as root:

# nano /etc/mysql/my.cnf

Tomorrow, we will start to plow through this file for optimization tweaks.

“DBAs and developers need solutions that help them manage their MySQL servers efficiently and allow them to identify performance issues before they become expensive, time-consuming problems,” said Tomas Ulin, director, MySQL Development, Oracle.

MySQL is one of the most widely-used database servers on the Web, and most web hosting providers offer it. While the underlying code for the database software is free and open source, there is also a commercially licensed version. MySQL was owned by Sun Microsystems until Oracle recently bought Sun and all of its software products.

Source: MarketWatch

Because it does not run via a sever, SQLite does not require the configuration and maintenance of other database systems. As a result, it is considered light and easy to use. Rather than running on a server, the database code is linked directly with the software using it. The library itself is small and can be installed in smaller installations.

According to their website, SQLite is the most often deployed database engine used in many web applications. It is free and open source, without a license, released into the public domain. You can download the libraries at the SQLite website.

Regardless of the scenario, selecting multiple database tables in the same query is a little more tricky. Here is a syntax that worked for me. First connect to your database the way you normally would, then enter your query like this:

$result = mysql_query("SELECT * FROM table1, table2 ");

Replace “table1” and “table2” with the actual names of your tables. Next, you can show rows from both tables, but if any of the rows have the same names in both tables, you will have to specify them specifically in the query.

Finally, display the results however you like:

while($row = mysql_fetch_array($result))
{
echo "<div id='corn'> ";
echo $row['corn'];
echo "</div> <div id='wheat'> ";
echo $row['wheat'];
echo "</div> ";

For more information on MySQL Select, see w3schools.com
Photo: Wikimedia Commons

To create a new table, follow these steps:

1. Login to your phpMyAdmin installation either through your control panel or directly.

2. On the left, click the database you want to manipulate.

3. At the bottom, underneath the current tables, find “Create new table on database” and enter the name and number of fields each row will have.

4. Enter the field names (each row will have a name assigned to it)

5. Select the data type. The default INT is for integer (i.e. a number). You can see a complete lists of data types on the mysql website

6. Select a maximum length or leave it blank

7. Set the type of collation, essentially the encoding, such as UTF-8.

8. When you have all of the information inputed, scroll to the bottom and click “Save”.

With that, you are all finished with your first table.

1. Login to phpMyAdmin either through your server’s control panel or directly.

Note: Some panels, such as cPanel require you to create databases through their interface. If so, follow their instructions

2. In the main Home section, look for “MySQL localhost“, and under “Create new database”, enter the name you want to use

3. Click “Create”

That is all it takes! You now have a new database. To assign users to the database, click the “Privileges” tab while you are still on that database’s page. Once you have the permissions you want, you can add, delete, and configure databases with relative ease.

Linux has two commands that make searching a little easier: locate and slocate. Unlike other find utilities, locate searches through a database that contains information about the filesystem, bringing up the search results almost instantaneously. The command to update the database is called “updatedb”, and many Linux distributions have the command run via cron every day.

The alternative version of locate, called slocate, is a security-enhanced version that only allows the user to find files he or she has the permission to access. While locate is a great tool for finding things on a server, it does have its issues. For one, you will only find files that were added or changed prior to the last updatedb execution. Furthermore, the very process of updating the database can be taxing on the server, even if it is only once a day. For the right situations, however, locate is a very useful Linux tool.

Photo Source: Flickr