The user password in MySQL is stored in the user table, the password reset is actually to change the value of record in this table. To change the password in case the password is forgotten, the idea is to bypass the authentication of MySQL and get into the system and update the record password value with SQL command.In MySQL 5, one can start MySQL service with --skip-grant-tables option, this option will tell the service to skip loading the grant tables when starting, hence the root user can login with empty password.mysqld –skip-grant-tables After login, can run below SQL command t...

When working with Hibernate and MySQL, sometimes some exceptions will be thrown after sometime. The exception may seem like :java.sql.SQLException: Data source rejected establishment of connection, message from server: "Too many connections"This means there are too many active connections on the MySQL, you can useSHOW STATUS LIKE '%Threads_connected%';to check the active connections to MySQL. If you want to change the maximum connections allowed to MySQL. You can execute:set global max_connections = [num];You may forget to manually call session.close() methods iin your codes. If you have done ...

Yesterday, my friend Liu Bing asked me a question about how to select top 3 values for each person in a database table using SQL. I think this question is interesting and it deserves some thoughts. Here I record down how to solve this issue.Assume we have a table which has two columns, one column contains the names of some people and the other column contains some values related to each person. One person can have more than one value. Each value has a numeric type. The question is we want to select the top 3 values for each person from the table. If one person has less than 3 values, we select...

To connect to MySQL database on Windows through Command line, there are some steps to be followed.1. You need to start the MySQL service, you can go to Start->Control Panel->System and Securities->Administrative Tools->Component Service->Services(local), then on the right panel, you can find one service name called MySQL and you should start this service2. Go the the MySQL installation folder, which is something like this : C:\Program Files\MySQL\MySQL Server 5.1. In this folder, find the bin folder.3. Open a command console and change the working directory to C:\Program Fi...

DbVisualizer is a very popular GUI application to view the data stored on a database. It supports various databases such as Oracle, MySQL etc. It relies on different database drivers to connect to the database server and access the data stored there. In this post, we will try to solve one problem when accessing the latest MySQL database(8.0+) through DbVisualizer. MySQL database starting from 8.0 has lots of changes which may not be compatible with old version of software or libraries which interact with it. There are also lots of issues reported while accessing the 8.0+ version of MySQL ...

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, ...