Why there is a difference between table and view?

Question

CREATE TABLE SK_ABC (ABC VARCHAR2(10),BBC NUMBER, CCD VARCHAR2(100), DDC DATE);
CREATE OR REPLACE VIEW SK_ABC_V
AS SELECT ABC,BBC,SubStr(CCD,1,40) CCD FROM SK_ABC;after this am seeing CCD length in view as 160 in database. am expecting length as 40 or atleast it should give me 100 as table ccd data length is 100, but it is showing me as 160 is bit surprised...
can any one please explain me?
SELECT table_Name,column_name,data_length,column_id,char_used FROM ALL_TAB_COLS WHERE TABLE_NAME LIKE 'SK%' ORDER BY TABLE_nAME,COLUMN_ID;
TABLE_NAME COLUMN_NAME DATA_LENGTH COLUMN_ID CHAR_USED
SK_ABC         ABC                   10                   1                  B
SK_ABC         BBC                   22                   2  
SK_ABC         CCD                  100                  3                  B
SK_ABC         DDC                     7                  4  
SK_ABC_V     ABC                    10                  1                   B
SK_ABC_V     BBC                     22                  2  
SK_ABC_V     CCD                    160                 3                   B

Answer 1

Hi,
This,
SubStr(CCD,1,40)You are taking 40 characters from CCD. You are probably using a multi byte character set, so the column will be 160 bytes. Your output shows char_used = B, that means length of column is taken in bytes.
Edit: Key word is NLS_LENGTH_SEMANTICS
http://download.oracle.com/docs/cd/E11882_01/appdev.112/e10766/tdddg_globalization.htm#TDDDG62910
I think the right thing would be to use char semantics when using multi byte character sets
Regards
Peter
Edited by: Peter on May 10, 2011 3:26 AM