These settings apply server-wide and apply as the defaults for databases created by any application, and for tables created in those databases. Specify character settings at MySQL configuration time. It is unnecessary to use --character-set-server and --collation-server to specify those defaults at server startup. Regardless of how you configure the MySQL character set for application use, you must also consider the environment within which those applications execute.
For example, if you send statements using UTF-8 text taken from a file that you create in an editor, you should edit the file with the locale of your environment set to UTF-8 so that the file encoding is correct and so that the operating system handles it correctly.
If you use the mysql client from within a terminal window, the window must be configured to use UTF-8 or characters may not display properly.
For a script that executes in a Web environment, the script must handle character encoding properly for its interaction with the MySQL server, and it must generate pages that correctly indicate the encoding so that browsers know how to display the content of the pages. Character Sets and Collations in General. Specifying Character Sets and Collations. Collation Naming Conventions. Server Character Set and Collation.
Database Character Set and Collation. Table Character Set and Collation. Column Character Set and Collation. Examples of Character Set and Collation Assignment. Connection Character Sets and Collations. Configuring Application Character Set and Collation. Table Character Set and Collation. Column Character Set and Collation.
Examples of Character Set and Collation Assignment. Connection Character Sets and Collations. Configuring Application Character Set and Collation. Column Character Set Conversion. Character Set and Collation Compatibility. Collation Coercibility in Expressions. Examples of the Effect of Collation. The utf8 Character Set Alias for utf8mb3.
Supported Character Sets and Collations. One is that some other languages uses more bytes that needed; another is that scanning a string is relatively expensive as you must decode each character to know where the next character begins.
The table shows how there clearly are some relations between these character sets, but also how only UTF-8 can represent all of the four test characters. So, from this comparison the strengths of UTF-8 is starting to show, but also the weaknesses. Until MySQL 8.
This was a convenient character set in many ways, for example it was fixed width, so finding the Nth character in a string was fast and it could store text for most Western European languages. However as discussed, Latin-1 is not what is used in this day and age — the World has moved on to UTF So, in MySQL 8. Stop a minute — what is utf8mb4? How does that differ from UTF-8 that was discussed in the previous section?
Well, it is the same thing. Internal temporary tables are for example used to store the result of subquery and for sorting. The MEMORY storage engine only supports fix width columns, so a varchar 10 column would be treated as a char 10 column in an in-memory internal temporary table.
With utf8mb4 that would mean 40 bytes, with the choice of a 3-byte implementation it would mean 30 bytes. Furthermore, until the emergence of emojis, it was rarely required to use more than three bytes in UTF Anyway, MySQL has support for a wide range of character sets to suite your specific need. In MySQL 8 there are a total of 41 character sets to choose from. Notice how there are several UTF and other Unicode character sets including utf8 and utf8m4. The utf8 character set is the 3-byte implementation.
The name utf8 has now been deprecated in favour of utf8mb3 to make it specific that you are using an implementation that can at most use three bytes per character.
The table has four columns: The character set name, the default collation, a description, and the maximum number of bytes per character. The first and the two last of the columns are clear enough, but what is the collation?
0コメント