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  1. 10 years ago by spirit
    You can check and compare sort orders provided by these two collations here:
    utf8_general_ci is a very simple collation. What it does - it just
    - removes all accents
    - then converts to upper case
    and uses the code of this sort of "base letter" result letter to compare.
    For example, these Latin letters: ÀÁÅåāă (and all other Latin letters "a" with any accents and in any cases) are all compared as equal to "A".
    utf8_unicode_ci uses the default Unicode collation element table (DUCET).
    The main differences are:
    1. utf8_unicode_ci supports so called expansions and ligatures, for example: German letter ß (U+00DF LETTER SHARP S) is sorted near "ss" Letter Œ (U+0152 LATIN CAPITAL LIGATURE OE) is sorted near "OE".
    utf8_general_ci does not support expansions/ligatures, it sorts all these letters as single characters, and sometimes in a wrong order.
    2. utf8_unicode_ci is *generally* more accurate for all scripts. For example, on Cyrillic block: utf8_unicode_ci is fine for all these languages: Russian, Bulgarian, Belarusian, Macedonian, Serbian, and Ukrainian. While utf8_general_ci is fine only for Russian and Bulgarian subset of Cyrillic. Extra letters used in Belarusian, Macedonian, Serbian, and Ukrainian
    are sorted not well.
    +/- The disadvantage of utf8_unicode_ci is that it is a little bit slower than utf8_general_ci.
    So when you need better sorting order - use utf8_unicode_ci, and when you utterly interested in performance - use utf8_general_ci.
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