Converting Long to Varchar2

Question

I am trying to insert into varchar2 column from a long column. here is the below example, TEXT.TEXT_COL = VARCHAR2(4000) and NOTE.TEXT_NOTE = LONG.

Answer 1

Converting from long to varchar2 right away using a single statement is not possible, as long has certain restrictions.

You can either Create a temporary table or use PL/SQL code to solve your problem:

• Temporary Table:

  CREATE TABLE TABLE2 AS SELECT TO_LOB(COLUMN1) COLUMN FROM TABLE1;

• PL/SQL Code:

  DECLARE
    VAR1 LONG;
    VAR2 VARCHAR2(4000);
  BEGIN
    SELECT TEXT INTO VAR1 FROM USER_VIEWS WHERE ROWNUM = 1;  
    VAR2 := SUBSTR(VAR1, 1, 4000);
    DBMS_OUTPUT.PUT_LINE(VAR2);
  END;
  

Answer 2

It looks like Oracle internally converts LONG to something else (probably CLOB) when you select LONG in FOR loop. I did not find any explanations in Oracle documentation, but this works

BEGIN
  FOR V IN (SELECT ROWID,TEXT_NOTE FROM NOTE)
  LOOP
    INSERT INTO TEXT VALUES(V.ROWID, SUBSTR(V.TEXT_NOTE, 1, 4000) );   
  END LOOP;
  COMMIT;
END;

This is an example how to copy all views from another schema to your schema

BEGIN
  FOR V IN (SELECT VIEW_NAME, TEXT_LENGTH, TEXT FROM ALL_VIEWS WHERE OWNER = 'PROD')
  LOOP
    EXECUTE IMMEDIATE 'CREATE OR REPLACE FORCE VIEW '||V.VIEW_NAME||' AS '||SUBSTR(V.TEXT, 1, V.TEXT_LENGTH);
    DBMS_OUTPUT.PUT_LINE('View '||V.VIEW_NAME||' created');
  END LOOP;
END;

For some reason it only works for FOR loop and does not work if you use WITH or select from another query

INSERT INTO TEXT
WITH V AS(SELECT ROWID ROW_ID,TEXT_NOTE FROM NOTE)
SELECT V.ROW_ID, SUBSTR(V.TEXT_NOTE, 1, 4000) FROM V; 

INSERT INTO TEXT
SELECT ROW_ID, SUBSTR(TEXT_NOTE, 1, 4000) 
FROM (SELECT ROWID ROW_ID,TEXT_NOTE FROM NOTE); 

Both inserts raise the same error

ORA-00932: inconsistent datatypes: expected CHAR got LONG