Having problem with to_lob function

Question

Hi,
Oracle DB version: 10.2.0.1.0
Tools being used: SQL Developer and SQLPlus (I have tried the query on both)
Create table test
col_xml LONG
...Note: We cannot convert this column to CLOB permanently because we just don't have the right to do that. :-(
Now, the problem is, I'm trying to convert this LONG into a CLOB using the TO_LOB function but still getting this error:
select TO_LOB(col_xml) from test;
ERROR at line 1:
ORA-00932: inconsistent datatypes: expected - got LONGBy the way, our main goal is to query this column so that we could filter the rows that we need.
Sort of:
select TO_LOB(col_xml) from test where TO_LOB(col_xml) like '%criteria%';Have I missed something or any idea on how to make my goal possible. The TO_LOB function is pretty simple but I don't know why it doesn't work in our my environment.
Suggestion/Ideas/Links to learning materials is high appreciated (Prefer oracle sites, message boards and forums are blocked by the firewall :-( ).
Thanks.

Answer 1

Spongebob wrote:
Follow up question: This TO_LOB function looks simple and easy to use but as shown above in my post it throws an error message. Have I missed something or is there something in our environment that affected the behavior of this function?Have a look at Oracle® Database SQL Language Reference.
There are several limitations with this function. It boils down to the following:
"<i>Before using this function, you must create a LOB column to receive the converted LONG values. To convert LONG values, create a CLOB column. To convert LONG RAW values, create a BLOB column.</i>"
So in other words, this function needs a destination LOB to write the LONG content into. It does not dynamically create the destination LOB/CLOB.
So you cannot do this as there is no explicit LOB definition to receive the converted LONG content:
SQL> select TO_LOB(text) from all_views where owner = 'SYSTEM' and view_name = 'PRODUCT_PRIVS';
select TO_LOB(text) from all_views where owner = 'SYSTEM' and view_name = 'PRODUCT_PRIVS'
ERROR at line 1:
ORA-00932: inconsistent datatypes: expected - got LONGBut if we create a destination LOB, we can use the function. E.g.
SQL> create table view_text( view_name varchar2(30), view_sql clob );
Table created.
SQL> insert into view_text select view_name, TO_LOB(text) from all_views where owner = 'SYSTEM' and view_name = 'PRODUCT_PRIVS';
1 row created.
SQL> The bottom line to this is: LONG IS AN EVIL DATA TYPE.
It should not be used. It dates back to Oracle 7. We are now at 11g. Several versions later. Still using the LONG data type in applications should be dealt with swiftly and harshly using the old lead pipe. Even a legacy app would have undergone several updates since Oracle v7. And that would have provided ample opportunity to convert from the horrible LONG data type to LOB.