Urgent!!! Modify column of a table having records

Question

Dear all,
I have a table with a column VARCHAR2(12) and I need to modify this column into VARCHAR2(9) without losing any data! s there any workaround?
Thanx a lot!!

Answer 1

This code was posted in one of the previous Oracle magazines:
The Pl/Sql procedure to rename the column must be compiled in to the database you require to rename columns in - one note I would run this as SYS:
create or replace procedure RenameColumn
(pUserName varchar2,
pTableName varchar2,
pOldColumnName varchar2,
pNewColumnName varchar2
is
vUserName dba_users.userName%type :=
upper(ltrim(rtrim(pUserName)));
vTableName dba_tables.table_name%type :=
upper(ltrim(rtrim(pTableName)));
vOldColumnName dba_tab_columns.column_name%type :=
upper(ltrim(rtrim(pOldColumnName)));
vNewColumnName dba_tab_columns.column_name%type :=
upper(ltrim(rtrim(pNewColumnName)));
vErrorMessage varchar2(4000);
eNotAuthorizedUser exception; /* -20101 */
eInvalidUser exception; /* -20102 */
eInvalidTable exception; /* -20103 */
eInvalidOldColumn exception; /* -20104 */
eInvalidNewColumn exception; /* -20105 */
cursor csrCheckUser
(pUser dba_users.userName%type)
is
select '1'
from dba_users
where userName = pUser;
cursor csrCheckTable
(pUser dba_tables.owner%type,
pTable dba_tables.table_name%type)
is
select '1'
from dba_tables
where owner = pUser
and table_name = pTable;
cursor csrCheckExistingColumn
(pUser dba_tables.owner%type,
pTable dba_tables.table_name%type,
pColumn dba_tab_columns.column_name%type)
is
select '1'
from dba_tab_columns
where owner = pUser
and table_name = pTable
and column_name = pColumn;
vDummy char(1);
begin
if user <> 'SYS'
then
raise eNotAuthorizedUser;
end if;
/* Check the value of vUserName */
if vUserName is null
then
raise eInvalidUser;
end if;
open csrCheckUser(vUserName);
fetch csrCheckUser into vDummy;
if csrCheckUser%notfound
then
close csrCheckUser;
raise eInvalidUser;
end if;
close csrCheckUser;
/* Check the value of vTableName */
if vTableName is null
then
raise eInvalidTable;
end if;
open csrCheckTable(vUserName, vTableName);
fetch csrCheckTable into vDummy;
if csrCheckTable%notfound
then
close csrCheckTable;
raise eInvalidTable;
end if;
close csrCheckTable;
/* Check the value of vOldColumnName */
if vOldColumnName is null
then
raise eInvalidOldColumn;
end if;
open csrCheckExistingColumn(vUserName, vTableName, vOldColumnName);
fetch csrCheckExistingColumn into vDummy;
if csrCheckExistingColumn%notfound
then
close csrCheckExistingColumn;
raise eInvalidOldColumn;
end if;
close csrCheckExistingColumn;
/* Check the value of vNewColumnName */
if vNewColumnName is null
then
raise eInvalidNewColumn;
end if;
open csrCheckExistingColumn(vUserName, vTableName, vNewColumnName);
fetch csrCheckExistingColumn into vDummy;
if csrCheckExistingColumn%found
then
close csrCheckExistingColumn;
raise eInvalidNewColumn;
end if;
close csrCheckExistingColumn;
/* Update the row in col$ Oracle dictionary */
update col$
set name = vNewColumnName
where (obj#, col#) in
(select obj#,
col#
from col$
where name = vOldColumnName
and obj# = (select obj#
from obj$
where name = vTableName
and owner# = (select user_id
from dba_users
where username = vUserName)));
commit;
exception
when eNotAuthorizedUser
then
vErrorMessage := 'User ' || user ||
' is not authorized to run this procedure.';
raise_application_error(-20101, vErrorMessage);
when eInvalidUser
then
vErrorMessage := 'Invalid user name: ' ||
pUserName || '.';
raise_application_error(-20102, vErrorMessage);
when eInvalidTable
then
vErrorMessage := 'Invalid table name: ' ||
pTableName || '.';
raise_application_error(-20103, vErrorMessage);
when eInvalidOldColumn
then
vErrorMessage := 'Invalid old column name: ' ||
pOldColumnName || '.';
raise_application_error(-20104, vErrorMessage);
when eInvalidNewColumn
then
vErrorMessage := 'Invalid new column name: ' ||
pNewColumnName || '.';
raise_application_error(-20105, vErrorMessage);
end RenameColumn;
Once you have the above in and compiled okay then you can rename you column names by:
begin
RenameColumn('SCOTT', 'EMPTEST', 'SAL', 'SALARY');
end;
also while still connected as SYS, note the parameters SCOTT should be the schema owner which contains the table, EMPTEST is the table name which contains the column, SAL is the old column name and SALARY is the new column name.
Have fun.