We cannot directly convert the data type VARCHAR2 to CLOB(Character Large OBject). Using below two options, we can able to covert it.
Option 1:
Step 1 : Convert the VARCHAR2 To LONG Data Type
Step 2 : Convert the LONG to CLOB Data Type.
Example:
Step 1: ALTER TABLE YOUR_TABLE_NAME MODIFY(Your_Column_Name LONG);
Step 2: ALTER TABLE YOUR_TABLE_NAME MODIFY(Your_Column_Name CLOB;
Option 2:
Step 1: Add a new column as CLOB
Step 2: UPDATE VARCHAR2 date to CLOB column
Step 3: DROP VARCHAR column
Step 4: Rename CLOB column to VARCHAR column name