mysql's collation roughly means character sorting.
First, characters are inherently size-insensitive, so a rule of character order is required for character >, =, <operations.collation does this either by setting the character order of a table or by setting the character order of a field separately.A character type that has multiple character orders, such as:
Below is the character order for UTF8.
utf8_general_ci utf8 33 Yes Yes 1 utf8_bin utf8 83 Yes 1 utf8_unicode_ci utf8 192 Yes 8 utf8_icelandic_ci utf8 193 Yes 8 utf8_latvian_ci utf8 194 Yes 8 utf8_romanian_ci utf8 195 Yes 8 utf8_slovenian_ci utf8 196 Yes 8 utf8_polish_ci utf8 197 Yes 8 utf8_estonian_ci utf8 198 Yes 8 utf8_spanish_ci utf8 199 Yes 8 utf8_swedish_ci utf8 200 Yes 8 utf8_turkish_ci utf8 201 Yes 8 utf8_czech_ci utf8 202 Yes 8 utf8_danish_ci utf8 203 Yes 8 utf8_lithuanian_ci utf8 204 Yes 8 utf8_slovak_ci utf8 205 Yes 8 utf8_spanish2_ci utf8 206 Yes 8 utf8_roman_ci utf8 207 Yes 8 utf8_persian_ci utf8 208 Yes 8 utf8_esperanto_ci utf8 209 Yes 8 utf8_hungarian_ci utf8 210 Yes 8 utf8_sinhala_ci utf8 211 Yes 8 utf8_german2_ci utf8 212 Yes 8 utf8_croatian_ci utf8 213 Yes 8 utf8_unicode_520_ci utf8 214 Yes 8 utf8_vietnamese_ci utf8 215 Yes 8 utf8_general_mysql500_ci utf8 223 Yes 1
mysql character order follows naming conventions
With_ci (indicating case insensitive)
With_cs (case sensitive)
With_bin (for comparison with coded values)
CREATE TABLE `issue_message` ( `id` int(11) NOT NULL AUTO_INCREMENT, `content` varchar(255) NOT NULL, PRIMARY KEY (`id`), ) ENGINE=MyISAM DEFAULT CHARSET=utf8;
The two SQLs below this table will produce the same result
select * from issue_message where content = 'Yes' select * from issue_message where content = 'yes'
If you change to the following definition:
CREATE TABLE `issue_message` ( `id` int(11) NOT NULL AUTO_INCREMENT, `content` varchar(255) NOT NULL COLLATE utf8_bin, PRIMARY KEY (`id`), ) ENGINE=MyISAM DEFAULT CHARSET=utf8;
Then the two sql results will be different.
Therefore, if character case is sensitive, it is best to set the default utf8_general_ci in the database to utf8_bin.