Changing data type on a field with populated data

Question

Hi
I have a table that has already been populated
i wish to change the data type of one of the fields from number to varchar2
this field has the same value you in it throughout
value = 2005 and i wish to change it to 2005/06
What is the best way to do this ?
thanks

Answer 1

As stated in the user guide, you can change the datatype of a column only when the value of this column is NULL in all existing rows. One workaround (in 10g) would be to add another column, update the new column, drop the old column and rename the new column to the old column's name. Here's an example:
CREATE TABLE test (col1 NUMBER(8));
INSERT INTO test VALUES (2005);
COMMIT;
ALTER TABLE test add (col2 VARCHAR2(8));
UPDATE test
   SET col2 = TO_CHAR(col1) || '/06';
COMMIT;
ALTER TABLE test DROP (col1);
ALTER TABLE test RENAME COLUMN col2 TO col1;C.