MySQL Unicode character set has following collations mainly:
- xxx_bin: compare all characters by these code point as weight.
- xxx_general_ci: compare almost characters by these code point as weight.
- xxx_unicode_ci: compare all characters by these collating weight.
ref. http://dev.mysql.com/doc/refman/5.6/en/charset-unicode-sets.html
When xxx is utf8, can treat only BMP characters.