一.官網的說明

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http://download.oracle.com/docs/cd/E11882_01/server.112/e26088/functions088.htm#SQLRF00658

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Purpose

The?LENGTH?functionsreturn the length of?char.?LENGTH?calculates length usingcharacters as defined by the input character set.?

???? --返回以字符為單位的長度.

LENGTHB?usesbytes instead of characters.?

???? --返回以字節為單位的長度.

LENGTHC?usesUnicode complete characters.?

???? --返回以Unicode完全字符為單位的長度.

LENGTH2?usesUCS2 code points.?

???? --返回以UCS2代碼點為單位的長度.

LENGTH4?usesUCS4 code points.

? ? --返回以UCS4代碼點為單位的長度.

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char?can beany of the data types?char,?varchar2,?nchar,?nvarchar2,?clob,or?nclob.

The exceptionsare?LENGTHC,?LENGTH2, and?LENGTH4, which do not allow char?tobe a?CLOB?or?NCLOB. The return value is of data type?NUMBER.If?char?has data type?CHAR, then the length includes all trailingblanks. If?char?is null, then this function returns null.

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Restriction on LENGTHB?(Lengthb函數的限制)

The?LENGTHB?functionis supported for single-byte LOBs only. It cannot be used with?CLOB?and?NCLOB?datain a multibyte character set.

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Examples

The followingexample uses the?LENGTH?function using a single-byte databasecharacter set:

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SELECT LENGTH('CANDIDE') "Length incharacters" FROM DUAL;

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Length in characters

--------------------

7

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The next example assumes a double-bytedatabase character set.

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SELECT LENGTHB ('CANDIDE') "Length inbytes" FROM DUAL;

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Length in bytes

---------------

14

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二.示例說明

在不同的數據庫，因為字符集的不同，LENGTHB得到的值可能會不一樣。如ZHS16GBK采用兩個byte位來定義一個漢字。而在UTF8，采用3個byte。

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SYS@anqing1(rac1)> SELECT USERENV('LANGUAGE') FROM DUAL;

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USERENV('LANGUAGE')

----------------------------------------------------

AMERICAN_AMERICA.ZHS16GBK

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SQL>select length('安慶') from dual;

2

SQL>select lengthb('安慶') from dual;

4

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SQL>select length('AnQing') from dual;

6

SQL>select lengthb('AnQing') from dual;

6

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通過這個示例，我們可以看出來，Length 和 Lengthb 函數的一個重要用處，就是用來判斷記錄值里是否有中文內容。

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如果有中文，那么Length() != Lengthb()

如果沒有中文，那么Length() == Lengthb()

轉載于:https://www.cnblogs.com/toSeeMyDream/p/4741695.html

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