What does data_length column indicates in user_tab_cols dictionary view

Question

Hi all,
Version details
BANNER
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
CORE     11.2.0.2.0     Production
TNS for Solaris: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production
SQL> create table
  2  temp
  3  (
  4   id number(9),
  5   id2 number(22,9),
  6   name varchar2(100),
  7  name2 varchar2(10)
  8  );
Table created.
SQL> ALTER TABLE TEMP ADD ID3 NUMBER(30);
table altered
SELECT table_name, column_name, data_type, data_length LENGTH, data_scale,
    data_precision  PRECISION
  FROM user_tab_cols utc
WHERE utc.table_name = 'TEMP';
output :
TABLE_NAME COLUMN_NAM DATA_TYPE      LENGTH DATA_SCALE  PRECISION
TEMP       ID         NUMBER             22          0          9
TEMP       ID2        NUMBER             22          9         22
TEMP       NAME       VARCHAR2          100                     0
TEMP       NAME2      VARCHAR2           10                     0
TEMP       ID3        NUMBER             22          0         30
SQL> My Question is
Why the length of the column ID is 22 , scale is zero and why the precision is 9 even though i have not mention anything while creation .
If you see name,name2 column it is showing what ever size i have given .
Is oracle requires 22 bytes for storing number data types .
Please clarify this ........
Thanks,
P Prakash
Edited by: prakash on Feb 19, 2012 9:55 PM
Edited by: prakash on Feb 19, 2012 9:56 PM

Answer 1

NVL (data_precision, 0) PRECISION
nvl function replaces all nulls with what ever your given value.
Thanks,
surya