When doing website development with MySQL, we often need to do database backup and restore. For website, the data in database will grow quickly, so when we back up the database, the size of the generated sql file may be over 80MB which is the max allowed size when we want to import a sql file for restoring our database using phpMyAdmin. To workaround this limit, we need to review the documentation of phpMyAdmin. Fortunately, I found an online article written by David Pratt  which gave us a very simple solution to this problem.Find the config.inc.php file located in the phpmyadmin director...

If you want to debug the issue of "MySQL server has gone away", you can reproduce it with below steps:Modify configuration file:sudo vi /etc/mysql/my.cnf  Make below changes:[mysqld]  wait_timeout = 30  interactive_timeout = 30  Restart the service:sudo /etc/init.d/mysql restart  Write below PHP codes:$link = mysql_connect('127.0.0.1', 'root', 'root');  if (!$link) {      die('Could not connect: ' . mysql_error());  ...

For non-English websites, they often have to deal with character set and collation if they want to store data to and read data from databases with other languages. Character set tells the database which kind of character encoding scheme to use to store or read data, collation can be simply understood as a subset of character set, it tells the database how to sort data. We talk about working with character set and collation of MySQL today.  In MySQL, if we want to store Chinese, Japanese or other languages other than English, we may need to set the relative character set for the database, ...

For a big data system, one problem is the data access efficiency, one more problem is that the data insertion is very slow. We had a service system, the data loading process would take 4-5 hours. This time consuming operation is risky since if the program is interrupted during the loading process, it might be rerun, this will be troublesome. So it's necessary to improve the insertion efficiency for big data systems.Here we provide two optimization suggestions.1. Combine multiple insert statementCommon insert statement use is:INSERT INTO `insert_table` (`datetime`, `uid`,&nb...

There are times where running IF statements inside a query can be useful. MySQL provides a simple way to do this through the use of IF and CASE statements.The IF statement takes three arguments; the conditional, the true value and the false value. False and true values may be static values or column values. For example:SELECT IF(score > 100, 100, score) AS scoreFROM exam_resultsthis will return the value in the score column limited to a maximum value of 100. IF statements can also be nested:SELECT IF(score > 100, 100, IF(score < 0, 0, score))FROM exam_resultsCASE statements (s...

Sometimes if we want to run MySQL but we don't have phpMyAdmin installed. What should we do?On Windows we can run MySQL in following steps:Open Console Window->Type "mysqld -u root". This means we start the mysql server with username root. This program will handle all the communications between our console window and the actual data;After starting the server, we need to use a client to connect to the server and communicate with it. the mysql program is right for this. Next in the command console, we type "mysql -u root -p" to connect the server. By default, after the installation,the defaul...

In a previous post, we discussed how the various relational operators are implemented in relational database systems. If you have read that post, you probably still remember that there are a few alternative implementations for every operator. Thus, how should RDBMS determine which algorithm (or implementation) to use?Obviously, to optimize the performance for any query, RDBMS has to select the correct the algorithm based on the query. It would not be desirable to always use the same algorithm. Also, SQL is a declarative language (i.e., as a programmer we only declare what we want to ...

 The result of the lawsuit case war between Oracle and Google is clearer now. The court said that 9 lines of code of Android has violated intellectual property right, these 9 lines of code can be ignored relative to the number of codes for the whole Android system. But just like LinuxToy points out that the reasons why this case catches so much attention are : 1). The amount of money Oracle asked from Google is $1 billion; 2). The statement says Java language itself doesn't violate the intellectual property rights, but the used public API did.If Oracle wins the case, it means that API can...