Insert text on Column exceeding 4000 bytes

Question

Hi ,
I create a table with two columns
Create table A (B NUMBER ,C VARCHAR2(4000));
I cant insert a text into coulmn C as it exceed its maximum allwable size.
Please help .
Thanks.

Answer 1

VARCHAR2 in Oracle are limited to 4000 bytes. Anything longer you need to store as CLOB. Unfortunately, you can't alter column from VARCHAR2 to CLOB. You would have to do someting like:
SQL> alter table a rename column c to d
  2  /
Table altered.
SQL> alter table a add c clob
  2  /
Table altered.
SQL> update a set c = d;
0 rows updated.
SQL> alter table a drop column d;
Table altered.
SQL> desc a
Name                                                                     Null?    Type
B                                                                                 NUMBER
C                                                                                 CLOB
SQL> So now column C is CLOB, it retains all values of old VARCHAR2 column C and you can insert values > 4000:
SQL> insert into a values(1,to_clob(lpad('A',4000,'A')) || lpad('B',4000,'B'));
1 row created.
SQL> select length(c) from a
  2  /
LENGTH(C)
      8000
SQL> SY.