Convert VARCHAR2 to CLOB

Oracle Database Tips by Donald BurlesonMay 7, 2013

Question: I want to convert a varchar2 column to a clob column. What are the methods for redefining a varchar to a CLOB column?

Answer: Oracle provides several ways to convert a varchar column t a clob:

1 - use the to_clob built-in function:

create table t (col_1 clob);

insert into t values (to_clob('Hello world'));

2 - Simply copy the column and use implicit conversion from varchar2 to CLOB:

create table t (col_1 varchar2(100));

insert into t values('Hello world');

commit;

alter table t add (col_2 clob);

update t set col_2 = col_1; -- convert varchar2 to CLOB

alter table t drop column col_1;

alter table t rename column col_2 to col_1

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