Convert LONG into VARCHAR2 or some text datatype - sql

Question

As we all know LONG is deprecated in Oracle a long back but Oracle itself is still using this datatype in their views.
So if I have to change LONG into some kind of text datatype how can I achieve that.
I am trying to query this and getting error.
ORA-00932: inconsistent datatypes: expected - got LONG
Query -
SELECT NVL(ie.column_expression, ic.column_name)
from user_ind_columns ic left join user_ind_expressions ie on ic.index_name = ie.index_name and ic.table_name = ie.table_name
where ic.table_name = 'Some Table'

Answer 1

There are several methods, one such is create table using TO_LOB. It is designed to convert a LONG or LONG RAW column to a CLOB or BLOB, respectively. Other methods are using PL/SQL, DBMS_XMLGEN. You can also use TO_LOB in insert statements.
Let's see how to convert LONG into CLOB-
SQL> CREATE TABLE t (x INT, y LONG);
Table created.
SQL>
SQL> INSERT INTO t VALUES (1, RPAD('*',9,'!'));
1 row created.
SQL> INSERT INTO t VALUES (2, RPAD('*',9,'#'));
1 row created.
SQL> INSERT INTO t VALUES (3, RPAD('*',9,'#'));
1 row created.
SQL> COMMIT;
Commit complete.
SQL>
So, we have table t with column y s LONG data type.
SQL> CREATE TABLE t1
2 AS
3 SELECT * FROM t
4 /
SELECT * FROM t
*
ERROR at line 3:
ORA-00997: illegal use of LONG datatype
SQL>
We can see the LONG restriction.
Let's use TO_LOB to convert it into CLOB.
SQL> CREATE TABLE t1
2 AS
3 SELECT x,
4 to_lob(y) as y
5 FROM t
6 /
Table created.
SQL> desc t1;
Name Null? Type
----------------------------------------------------- -------- ------------------------------------
X NUMBER(38)
Y CLOB
SQL>
Now you have the same table with the LONG column converted to CLOB.

Answer 2

this is stupid (as in probably not efficient) but it works for samll lengths of y (ie < 2000 characters)..
CREATE TABLE t (x INT, y LONG);
INSERT INTO t VALUES (1, RPAD('*',9,'!'));
CREATE TABLE t1
AS
SELECT x,
regexp_substr(SYS.DBMS_XMLGEN.GETXML('select y from t where rowid = '''||rowid||''''),'<Y>(.*)</Y>',1,1,'in',1) y
FROM t
/
it works by using dbms_xmlgen to generate a clob based on the LONG column.. then substr-ing the value back out.
this only works for small contents of the LONG column. but that is all i had and this worked for me.

Answer 3

I had a similar need, to list the objects and their sizes (including info on columns used in indexes), and came with this solution:
select idx1.table_owner owner, idx1.table_name, idx1.index_name, listagg(nvl(idx1.column_expression,idx1.column_name),',') within group (order by idx1.column_position) column_name
from xmltable(
'/ROWSET/ROW'
passing (select dbms_xmlgen.getxmltype('select ic.table_owner, ic.table_name, ic.index_name, ic.column_position, ic.column_name, ie.column_expression
from all_ind_columns ic
left outer join dba_ind_expressions ie on ie.table_owner=ic.table_owner and ie.table_name=ic.table_name and ie.index_name=ic.index_name and ie.column_position=ic.column_position') from dual)
columns index_name varchar2(30) path 'INDEX_NAME'
, table_owner varchar2(30) path 'TABLE_OWNER'
, table_name varchar2(30) path 'TABLE_NAME'
, column_position number path 'COLUMN_POSITION'
, column_name varchar2(30) path 'COLUMN_NAME'
, column_expression varchar2(4000) path 'COLUMN_EXPRESSION') idx1
group by idx1.table_owner, idx1.table_name, idx1.index_name