mysql changes the encoding of the database

MySQL is a popular relational database management system that can be used for personal websites and small businesses, as well as large applications and enterprise-level software. MySQL uses UTF-8 encoding by default to support multi-language data storage, but sometimes you encounter database encoding problems, such as garbled characters or the inability to display Chinese characters properly. At this time, the MySQL database coding needs to be modified to solve these problems.

This article will introduce how to modify the MySQL database encoding. First, we need to understand the concepts of MySQL character set and encoding. The character set in MySQL refers to the character set that represents characters and text in the database, such as utf8, gbk, etc. Encoding refers to how these character sets are used for storage and transmission on computers.

Step 1: Back up the database

Be sure to back up the database before making any modifications to prevent accidental data loss. You can use the mysqldump command to back up the entire database to a SQL file, as shown below:

mysqldump -u username -p dbname > backup.sql

where username is the MySQL user name, dbname is the name of the database to be backed up, and backup.sql is the backup file name.

After the backup is completed, you can continue to modify the MySQL encoding.

Step 2: Check the database encoding

Use the following command to check the character set and encoding of the current database:

SHOW VARIABLES LIKE '%character%';

The results are as follows:

+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | utf8mb4                    |
| character_set_connection | utf8mb4                    |
| character_set_database   | utf8mb4                    |
| character_set_filesystem | binary                     |
| character_set_results    | utf8mb4                    |
| character_set_server     | utf8mb4                    |
| character_set_system     | utf8                       |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+

You can do it here As you can see, the character set and encoding of the current database are both utf8mb4. If you want to change it to gbk or other encoding, you need to proceed to the next step.

Step 3: Modify the database encoding

First you need to confirm the database name to be modified. Suppose you want to change the encoding of the database mydb to gbk, you can use the following command:

ALTER DATABASE mydb CHARACTER SET gbk;

You can use the following command to confirm whether the database encoding has been modified successfully.

SHOW CREATE DATABASE mydb;

Among them, mydb is the name of the database to be modified. If you see "DEFAULT CHARACTER SET gbk" in the output, it means that the database encoding has been modified successfully.

If there is already a data table in the database, its character set and encoding also need to be modified to the new target encoding. You can use the following command to modify a single data table:

ALTER TABLE mytable CONVERT TO CHARACTER SET gbk;

where, mytable is the name of the data table to be modified, and gbk is the target encoding.

If you need to modify the coding of multiple data tables at the same time, you can use the following command to modify it in batches:

ALTER DATABASE mydb CHARACTER SET gbk;
ALTER TABLE mytable1 CONVERT TO CHARACTER SET gbk;
ALTER TABLE mytable2 CONVERT TO CHARACTER SET gbk;
...

It should be noted that modifying the coding of the data table will change the coding of all columns in the data table. Character set and encoding, this means that the original data in the data table will be overwritten, so be sure to back up the data before performing modifications. In addition, if you want to query these data tables, you also need to use an encoding that matches its character set and encoding.

Step 4: Restart MySQL

After modifying the character set and encoding of the data table, you need to restart the MySQL service to ensure that the database modification has taken effect. You can use the following command to restart the MySQL server:

sudo systemctl restart mysql

You need to enter the password of the root user to execute this command.

Summary

Modifying the MySQL database encoding can solve problems related to character sets and encoding. This process can be completed by backing up the data, checking the character set and encoding, modifying the database encoding, and restarting MySQL. It should be noted that modifying the database encoding will affect all existing data tables in the database, so be sure to back up the data before operating.

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