問題描述

我可以閱讀 MySQL 文檔，而且非常清楚.但是，如何決定使用哪個字符集?整理對哪些數(shù)據(jù)有影響?

I can read the MySQL documentation and it's pretty clear. But, how does one decide which character set to use? On what data does collation have an effect?

我要求解釋這兩者以及如何選擇它們.

I'm asking for an explanation of the two and how to choose them.

推薦答案

來自 MySQL 文檔:

字符集是一組符號和編碼.collat??ion 是一組比較字符的規(guī)則字符集.讓我們做用一個例子區(qū)分清楚一個虛構(gòu)的字符集.

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.

假設(shè)我們有一個字母表四個字母:A"、B"、a"、b".我們給每個字母一個數(shù)字:'A' = 0，'B' = 1, 'a' = 2, 'b' = 3. 字母'A' 是一個符號，數(shù)字 0 是'A' 的編碼，以及組合所有四個字母及其encodings 是一個字符集.

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.

現(xiàn)在，假設(shè)我們要比較兩個字符串值，A"和B".這最簡單的方法是查看編碼:0 代表A"，1 代表'乙'.因?yàn)?0 小于 1，所以我們說A"小于B".現(xiàn)在，我們所擁有的剛剛完成的是對我們的字符集.整理是一個集合規(guī)則(在這種情況下只有一個規(guī)則):比較編碼."我們稱之為所有可能的排序規(guī)則中最簡單的一個二進(jìn)制整理.

Now, 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'. Now, 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.

但是如果我們想說小寫和大寫字母是相等的?那么我們將在至少有兩條規(guī)則:(1)對待小寫字母 'a' 和 'b' 作為相當(dāng)于A"和B"；(2) 那么比較編碼.我們稱之為不區(qū)分大小寫的排序規(guī)則.它是比二進(jìn)制復(fù)雜一點(diǎn)整理.

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.

在現(xiàn)實(shí)生活中，大多數(shù)字符集都有許多字符:不僅僅是A"和B"但是整個字母表，有時多個字母或東方文字具有數(shù)千個字符的系統(tǒng)，以及許多特殊符號和標(biāo)點(diǎn)符號.在現(xiàn)實(shí)生活中，大多數(shù)排序規(guī)則有很多規(guī)則:不只是不區(qū)分大小寫，但也口音不敏感(口音"是附加到字符的標(biāo)記，如德語 '?') 和多字符映射(例如?"='OE' 在兩個德語之一中排序規(guī)則).

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 case insensitivity but also accent insensitivity (an "accent" is a mark attached to a character as in German '?') and multiple-character mappings (such as the rule that '?' = 'OE' in one of the two German collations).

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