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 10.1 Character Sets and Collations in General
 =============================================
 
 A character set is a set of symbols and encodings. A collation is a set
 of rules for comparing characters in a character set. Let's make the
 distinction clear with an example of an imaginary character set.
 
 Suppose that we have an alphabet with four letters: ‘`A'’,
 ‘`B'’, ‘`a'’, ‘`b'’. We give each letter a number:
 ‘`A'’ = 0, ‘`B'’ = 1, ‘`a'’ = 2, ‘`b'’ = 3. The letter
 ‘`A'’ is a symbol, the number 0 is the *encoding* for ‘`A'’,
 and the combination of all four letters and their encodings is a
 *character set*.
 
 Suppose that we want to compare two string values, ‘`A'’ and
 ‘`B'’. The simplest way to do this is to look at the encodings: 0
 for ‘`A'’ and 1 for ‘`B'’. Because 0 is less than 1, we say
 ‘`A'’ is less than ‘`B'’. What we've just done is apply a
 collation to our character set. The collation is a set of rules (only
 one rule in this case): `compare the encodings.' We call this simplest
 of all possible collations a binary collation.
 
 But what if we want to say that the lowercase and uppercase letters are
 equivalent? Then we would have at least two rules: (1) treat the
 lowercase letters ‘`a'’ and ‘`b'’ as equivalent to ‘`A'’ and
 ‘`B'’; (2) then compare the encodings. We call this a
 case-insensitive collation. It's a little more complex than a binary
 collation.
 
 In real life, most character sets have many characters: not just
 ‘`A'’ and ‘`B'’ but whole alphabets, sometimes multiple
 alphabets or eastern writing systems with thousands of characters,
 along with many special symbols and punctuation marks.  Also in real
 life, most collations have many rules, not just for whether to
 distinguish lettercase, but also for whether to distinguish accents (an
 `accent' is a mark attached to a character as in German ‘`O"'’),
 and for multiple-character mappings (such as the rule that ‘`O"'’ =
 ‘`OE'’ in one of the two German collations).
 
 MySQL can do these things for you:
 
    * Store strings using a variety of character sets
 
    * Compare strings using a variety of collations
 
    * Mix strings with different character sets or collations in the
      same server, the same database, or even the same table
 
    * Allow specification of character set and collation at any level
 
 In these respects, MySQL is far ahead of most other database management
 systems. However, to use these features effectively, you need to know
 what character sets and collations are available, how to change the
 defaults, and how they affect the behavior of string operators and
 functions.
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