blocks|key|1544845|text|一个恰好有11个字节的空间，另一个恰好有11个字符。某些字符集，如Unicode变体，每个字符可能使用一个以上的字节，因此，根据编码的不同，11个字节字段的空间可能少于11个字符。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1544846|另请参阅http://www.joelonsoftware.com/articles/Unicode.html|offset|length|1544847|entityMap|0|LINK|mutability|MUTABLE|url|http://www.joelonsoftware.com/articles/Unicode.html^0|0|4|1F|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

One has exactly space for 11 bytes, the other for exactly 11 characters. Some charsets such as Unicode variants may use more than one byte per char, therefore the 11 byte field might have space for less than 11 chars depending on the encoding.

See also <a href="http://www.joelonsoftware.com/articles/Unicode.html" rel="noreferrer">http://www.joelonsoftware.com/articles/Unicode.html</a>

blocks|key|1759790|text|我不确定，因为我不是Oracle用户，但我假设不同之处在于您使用Unicode+(UTF-16/32)等多字节字符集。在这种情况下，11个字节可能占少于11个字符。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1759791|此外，对于重音字符或大小写，这些字段类型可能会有不同的处理方式，例如，'binaryField(ete)+=+"été"‘将不匹配，而’charField(+be+)=“été‘可能会匹配(同样不确定甲骨文)。|1759792|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

I am not sure since I am not an Oracle user, but I assume that the difference lies when you use multi-byte character sets such as Unicode (UTF-16/32). In this case, 11 Bytes could account for less than 11 characters.

Also those field types might be treated differently in regard to accented characters or case, for example 'binaryField(ete) = "été"' will not match while 'charField(ete) = "été"' might (again not sure about Oracle).

blocks|key|1544952|text|让我们假设数据库字符集是UTF-8，这是Oracle最新版本中的推荐设置。在这种情况下，有些字符需要超过1个字节才能存储在数据库中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1544953|如果将该字段定义为VARCHAR2(11+BYTE)，则Oracle最多可使用11个字节进行存储，但实际上您可能无法在该字段中存储11个字符，因为其中一些字符需要一个以上的字节来存储，例如非英语字符。|offset|length|style|CODE|1544954|通过将字段定义为VARCHAR2(11+CHAR)，您可以告诉Oracle它可以使用足够的空间来存储11个字符，而不管存储每个字符需要多少字节。单个字符可能最多需要4个字节。|1544955|entityMap^0|0|9|H|0|8|H|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@$D|N|E|O|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|P|8|@$D|Q|E|R|F|G]]|9|@]|A|$]]|$1|J|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|K|$]]

Let us assume the database character set is UTF-8, which is the recommended setting in recent versions of Oracle. In this case, some characters take more than 1 byte to store in the database.

If you define the field as <code>VARCHAR2(11 BYTE)</code>, Oracle can use up to 11 bytes for storage, but you may not actually be able to store 11 characters in the field, because some of them take more than one byte to store, e.g. non-English characters.

By defining the field as <code>VARCHAR2(11 CHAR)</code> you tell Oracle it can use enough space to store 11 characters, no matter how many bytes it takes to store each one. A single character may require up to 4 bytes.

blocks|key|1759902|text|简单地说，当您编写NAME+VARCHAR2(11+BYTE)时，该变量中只能容纳11个字节。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1759903|无论您使用的是哪种字符集，例如，如果您使用Unicode+(UTF-16)，那么在NAME中只能容纳名称大小的一半。|1759904|另一方面，如果您编写NAME+VARCHAR2(11+CHAR)，那么无论字符编码如何，NAME都可以支持11个字符。|1759905|如果未指定BYTE或CHAR，则缺省设置为BYTE|1759906|因此，如果编写NAME+VARCHAR2(4000+BYTE)并使用Unicode(UTF-16)字符编码，那么在NAME中只能容纳2000个字符|1759907|这意味着在BYTES中应用了对变量的大小限制，这取决于该变量中可以容纳多少个字符的字符编码。|1759908|entityMap^0|9|M|0|15|4|0|A|M|18|4|0|5|4|A|4|L|4|0|7|O|1L|4|0|5|5|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|C]]|D|@]|E|$]]|$1|J|3|K|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@]|E|$]]|$1|L|3|M|5|6|7|19|8|@$9|1A|A|1B|B|C]|$9|1C|A|1D|B|C]]|D|@]|E|$]]|$1|N|3|O|5|6|7|1E|8|@$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|P|3|-4|5|6|7|1H|8|@]|D|@]|E|$]]]|Q|$]]

In simple words when you write <code>NAME VARCHAR2(11 BYTE)</code> then only 11 Byte can be accommodated in that variable.
No matter which characters set you are using, for example, if you are using Unicode (UTF-16) then only half of the size of Name can be accommodated in <code>NAME</code>.
On the other hand, if you write <code>NAME VARCHAR2(11 CHAR)</code> then <code>NAME</code> can accommodate 11 CHAR regardless of their character encoding.
<code>BYTE</code> is the default if you do not specify <code>BYTE</code> or <code>CHAR</code>
So if you write <code>NAME VARCHAR2(4000 BYTE)</code> and use Unicode(UTF-16) character encoding then only 2000 characters can be accommodated in <code>NAME</code>
That means the size limit on the variable is applied in <code>BYTES</code> and it depends on the character encoding that how many characters can be accommodated in that vraible.

In Oracle, what is the difference between :

<pre><code>CREATE TABLE CLIENT
(
 NAME VARCHAR2(11 BYTE),
 ID_CLIENT NUMBER
)
</code></pre>

and

<pre><code>CREATE TABLE CLIENT
(
 NAME VARCHAR2(11 CHAR), -- or even VARCHAR2(11)
 ID_CLIENT NUMBER
)
</code></pre>

Difference between BYTE and CHAR in column datatypes

数据库

在Oracle中，以下各项有何不同：CREATE TABLE CLIENT( NAME VARCHAR2(11 BYTE), ID_CLIENT NUMBER)和CREATE TABLE CLIENT( NAME VARCHAR2(11 CHAR), -- or even VARCHAR2(11) ID_CLIENT ...

问BYTE和CHAR在列数据类型中的差异
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