【函数】Oracle函数系列（1）--字符函数1.6--length函数

3.0.6   length:求字符串长度

SELECT length('重庆贵阳30N重庆贵阳30N-77623') FROM dual;

SELECT length(77623) FROM dual;

SELECT length(sysdate),sysdate FROM dual;

SELECT length(1/2) FROM dual;

SELECT length('1/2'),

       length(1 / 2),

       1 / 2,

 length(0.5)

FROM   dual;

一、  

The LENGTH functions return the length of char. LENGTH calculates length usingcharacters as defined by the input character set.  --返回以字符为单位的长度.

LENGTHB usesbytes instead of characters.  --返回以字节为单位的长度.

LENGTHC usesUnicode complete characters. --返回以Unicode完全字符为单位的长度.

LENGTH2 usesUCS2 code points.--返回以UCS2代码点为单位的长度.

LENGTH4 usesUCS4 code points.  --返回以UCS4代码点为单位的长度.

char can be any of the data types CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The exceptions are LENGTHC, LENGTH2, and LENGTH4, which do not allow char to be a CLOB or NCLOB. The return value is of data type NUMBER. If char has data type CHAR, then the length includes all trailing blanks. If char is null, then this function returns null.

Restriction on LENGTHB The LENGTHB function is supported for single-byte LOBs only. It cannot be used with CLOB and NCLOB data in a multibyte character set.

Examples

The following example uses the LENGTH function using a single-byte database character set:

SELECT LENGTH('CANDIDE') "Length in characters"

  FROM DUAL;

Length in characters

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

                   7

The next example assumes a double-byte database character set.

SELECT LENGTHB ('CANDIDE') "Length in bytes"

  FROM DUAL;

Length in bytes

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

             14

SQL> select length('北京') from dual;

LENGTH('北京')

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

             2

SQL> select lengthb('北京') from dual;

LENGTHB('北京')

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

              6

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

LENGTHB('BEIJING')

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

                 7

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

LENGTH('BEIJING')

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

                7

值得一提的是：

在不同的数据库，因为字符集的不同，LENGTHB得到的值可能会不一样。如ZHS16GBK采用两个byte位来定义一个汉字。而在UTF8，采用3个byte。

--查看字符集语句

SQL> select * from nls_database_parameters where parameter='NLS_CHARACTERSET';

PARAMETER                      VALUE

select lengthb('齐'),length('齐') from dual

在计算单字节的字符串时。返回的值是相同的。

select lengthb('string'),length('string') from dual

2 、通过对同一个字符串的长度判断

lengthb(string)=length(string)

可以判断是否含有汉字。

例子

SELECT lengthb('齐'),

       length('齐')

FROM   dual;

SELECT l.code,

       length(l.code),

       lengthb(l.code),

       length2(l.code),

       length4(l.code),

       lengthc(l.code)

FROM   xb_link l

WHERE  length(l.code) != lengthb(l.code)

AND    length(l.code) < 20;

二、 判断字符串中是否含有汉字

参考：