- #Command mysql create database utf8 how to
- #Command mysql create database utf8 update
- #Command mysql create database utf8 code
Updating your databases and code might take some time, but it’s definitely worth the effort. Never use utf8 in MySQL - always use utf8mb4 instead. This will prompt for the root user’s password, after which all tables in all databases will be repaired and optimized. Luckily, this can easily be done in one go using the command-line mysqlcheck utility: $ mysqlcheck -u root -p -auto-repair -optimize -all-databases
You could run the following MySQL queries for each table you want to repair and optimize: # For each table
#Command mysql create database utf8 update
I didn’t do this right away after upgrading (I didn’t think it was necessary, as everything seemed to work fine at first glance), and ran into some weird bugs where UPDATE statements didn’t have any effect, even though no errors were thrown. Step 6: Repair and optimize all tablesĪfter upgrading the MySQL server and making the necessary changes explained above, make sure to repair and optimize all databases and tables. Note: The default character set and collation can be configured at some other levels as well. | collation_server | utf8mb4_unicode_ci |Īs you can see, all the relevant options are set to utf8mb4, except for character_set_filesystem which should be binary unless you’re on a file system that supports multi-byte UTF-8-encoded characters in file names, and character_set_system which is always utf8 and can’t be overridden. | collation_database | utf8mb4_unicode_ci | | collation_connection | utf8mb4_unicode_ci | PHP object injection vulnerability in WordPress SHOW VARIABLES WHERE Variable_name LIKE 'character\_set\_%' OR Variable_name LIKE 'collation%'.Here are some examples, all of which were discovered after publishing this write-up: Proper UTF-8 can encode 100% of all Unicode code points.Īs shown above, this behavior can lead to data loss, but it gets worse - it can result in security vulnerabilities. In fact, MySQL’s utf8 only allows you to store 5.88% ( (0x00FFFF + 1) / (0x10FFFF + 1)) of all possible Unicode code points. In total, that’s 1,048,575 possible code points you can’t use.
This doesn’t just affect the ? character, but more important symbols like U+01F4A9 PILE OF POO ( ?) as well. Since astral symbols (whose code points range from U+010000 to U+10FFFF) each consist of four bytes in UTF-8, you cannot store them using MySQL’s utf8 implementation. It can only store UTF-8-encoded symbols that consist of one to three bytes encoded symbols that take up four bytes aren’t supported. Turns out MySQL’s utf8 charset only partially implements proper UTF-8 encoding. | Warning | 1366 | Incorrect string value: '\xF0\x9D\x8C\x86' for column 'column_name' at row 1 | MySQL returned a warning message, too: mysql> SHOW WARNINGS The content got truncated at the first astral Unicode symbol, in this case ? - so, attempting to insert foo?bar actually inserted foo instead, resulting in data loss (and possibly introducing security issues see below). Mysql> SELECT column_name FROM database_name.table_name WHERE id = 9001 Query OK, 1 row affected, 1 warning (0.00 sec) Mysql> UPDATE database_name.table_name SET column_name = 'foo?bar' WHERE id = 9001 mysql> SET NAMES utf8 # just to emphasize that the connection charset is set to `utf8` The column I was trying to update had the utf8_unicode_ci collation, and the connection charset was set to utf8. While writing about JavaScript’s internal character encoding, I noticed that there was no way to insert the U+1D306 TETRAGRAM FOR CENTRE ( ?) symbol into the MySQL database behind this site. By using utf8, I’d be able to store any symbol I want in my database - or so I thought. MySQL’s utf8įor a long time, I was using MySQL’s utf8 charset for databases, tables, and columns, assuming it mapped to the UTF-8 encoding described above. This way, UTF-8 is optimized for the common case where ASCII characters and other BMP symbols (whose code points range from U+000000 to U+00FFFF) are used - while still allowing astral symbols (whose code points range from U+010000 to U+10FFFF) to be stored.
Symbols with lower numerical code point values are encoded using fewer bytes. UTF-8 is a variable-width encoding it encodes each symbol using one to four 8-bit bytes. (Not all of these Unicode code points have been assigned characters yet, but that doesn’t stop UTF-8 from being able to encode them.) The UTF-8 encoding can represent every symbol in the Unicode character set, which ranges from U+000000 to U+10FFFF.
#Command mysql create database utf8 how to
Alternative title: The things we do to store U+1F4A9 PILE OF POO ( ?) correctly.Īre you using MySQL’s utf8 charset in your databases? In this write-up I’ll explain why you should switch to utf8mb4 instead, and how to do it.