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LENGTH calculates length using characters as defined by the input character set. 
LENGTHB uses bytes instead of characters. 
VSIZE returns the number of bytes in the internal representation of expr.
LENGTHC uses Unicode complete characters. 
LENGTH2 uses UCS2 codepoints. 
LENGTH4 uses UCS4 codepoints 
select length('adfadºÏÀí') "bytesLengthIs" from dual --7
select lengthb('adfad') "bytesLengthIs" from dual --5
select lengthb('adfadºÏÀí') "bytesLengthIs" from dual --11
select vsize('adfadºÏÀí') "bytesLengthIs" from dual --11
select lengthc('adfadºÏÀí')"bytesLengthIs" from dual --7
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lengthb=vsize
lengthc=length
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a.¸ñʽ£ºVariable_name [constant] databyte [not null] [:=default expression]
b.±äÁ¿Óë³£Á¿ÉùÃ÷»ù±¾Ò»Ö£¬Ê¹ÓÃconstantÉùÃ÷µÄΪ³£Á¿£¬²»Ê¹ÓÃΪ±äÁ¿£¬²¢ÇÒ¸³ÖµÖ»ÄÜÔÚDECLAREÇøÓò¸³Öµ£»
c.ʹÓÃ%TYPEºÍ%ROWTYPEÉùÃ÷¿ÉÒÔʹ±äÁ¿µÄÀàÐÍÓë±íÖÐ×Ö¶ÎÀàÐÍ»òÕû¸ö¼Ç¼ÀàÐͱ ......

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1. ASCII
·µ»ØÓëÖ¸¶¨µÄ×Ö·û¶ÔÓ¦µÄÊ®½øÖÆÊý;
SQL> select ascii(A) A,ascii(a) a,ascii(0) zero,ascii( ) space from dual;
A A ZERO SPACE
--------- --------- --------- ---------
65 97 48 32
2. CHR
¸ø³öÕûÊý,·µ»Ø¶ÔÓ¦µÄ×Ö·û;
SQL> select chr(54740) zhao,chr(65) chr65 from dual;
ZH C
-- ......

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sqlplus;
sys /password as sysdba;
--²éÕÒÓû§ID£¨user#£©,Êý¾Ý¿âÀïÃæ´æ·ÅµÄÓû§¶¼ÊÇ´óд!
select user#,name,password from user$ where name ='FACT';
USER# NAME                      ......

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