TO_CLOB

TO_CLOB(lob_column | char)

-- Create a table named `tbl_nclob`.
CREATE TABLE tbl_nclob (
    -- Add a column named `COL1`. Set the column type to `NUMBER` and maximum precision to 38 digits.
    COL1 NUMBER(38),

    -- Add a column named `COL_CHAR`. Set the column type to `VARCHAR2` and maximum length to 100 characters.
    COL_CHAR VARCHAR2(100),

    -- Add a column named `COL_CLOB`. Set the column type to `CLOB` for storing long text data.
    COL_CLOB CLOB
);

obclient> DESC tbl_nclob;
+----------+---------------+------+-----+---------+-------+
| FIELD    | TYPE          | NULL | KEY | DEFAULT | EXTRA |
+----------+---------------+------+-----+---------+-------+
| COL1     | NUMBER(38)    | YES  | NULL | NULL    | NULL  |
| COL_CHAR | VARCHAR2(100) | YES  | NULL | NULL    | NULL  |
| COL_CLOB | CLOB          | YES  | NULL | NULL    | NULL  |
+----------+---------------+------+-----+---------+-------+
3 rows in set

obclient> UPDATE tbl_nclob SET col_clob = TO_CLOB (col_char);
Query OK, 1 row affected
Rows matched: 1  Changed: 1  Warnings: 0