- 9.1.10 Unicode Support
- 9.1.10.1 The ucs2 Character Set (UCS-2 Unicode Encoding)
- 9.1.10.2 The utf16 Character Set (UTF-16 Unicode Encoding)
- 9.1.10.3 The utf32 Character Set (UTF-32 Unicode Encoding)
- 9.1.10.4 The utf8 Character Set (Three-Byte UTF-8 Unicode Encoding)
- 9.1.10.5 The utf8mb3 “Character Set” (Alias for utf8)
- 9.1.10.6 The utf8mb4 Character Set (Four-Byte UTF-8 Unicode Encoding)
The character set named utf8 uses a maximum
of three bytes per character and contains only BMP characters.
As of MySQL 5.5.3, the utf8mb4 character
set is available and supports supplemental characters:
For a BMP character,
utf8andutf8mb4have identical storage characteristics: same code values, same encoding, same length.For a supplementary character,
utf8cannot store the character at all, whileutf8mb4requires four bytes to store it. Sinceutf8cannot store the character at all, you do not have any supplementary characters inutf8columns and you need not worry about converting characters or losing data when upgradingutf8data from older versions of MySQL.
utf8mb4 is a superset of
utf8, so for an operation such as the
following concatenation, the result has character set
utf8mb4 and the collation of
utf8mb4_col:
SELECT CONCAT(utf8_col, utf8mb4_col);
Similarly, the following comparison in the
WHERE clause works according to the
collation of utf8mb_col:
SELECT * FROM utf8_tbl, utf8mb4_tbl WHERE utf8_tbl.utf8_col = utf8mb4_tbl.utf8mb4_col;
Tip
To save space with UTF-8, use
VARCHAR instead of
CHAR. Otherwise, MySQL must
reserve three (or four) bytes for each character in a
CHAR CHARACTER SET utf8 (or
utf8mb4) column because that is the
maximum possible length. For example, MySQL must reserve 40
bytes for a CHAR(10) CHARACTER SET
utf8mb4 column.
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