[oracle] ORA-00932: inconsistent datatypes: expected - got CLOB

Considering that TEST_SCRIPT is a CLOB why when I run this simple query from SQL*PLUS on Oracle, I get the error:

ORA-00932: inconsistent datatypes: expected - got CLOB

I have been reading a lot of questions about the same error but none of those is running a direct query from SQLPLUS

    UPDATE IMS_TEST 
       SET TEST_Category  = 'just testing'  
     WHERE TEST_SCRIPT    = 'something'
       AND ID             = '10000239' 

Full example:

SQL> create table ims_test(
  2  test_category varchar2(30),
  3  test_script clob,
  4  id varchar2(30)
  5  );

Table created.

SQL> insert into ims_test values ('test1','something','10000239');

1 row created.

SQL> UPDATE IMS_TEST
  2  SET TEST_Category  = 'just testing'
  3  WHERE TEST_SCRIPT    = 'something'
  4  AND ID             = '10000239';
WHERE TEST_SCRIPT    = 'something'
      *
ERROR at line 3:
ORA-00932: inconsistent datatypes: expected - got CLOB

I found that selecting a clob column in CTE caused this explosion. ie

with cte as (
    select
        mytable1.myIntCol,
        mytable2.myClobCol
    from mytable1
    join mytable2 on ...
)
select myIntCol, myClobCol
from cte
where ...

presumably because oracle can't handle a clob in a temporary table.

Because my values were longer than 4K, I couldn't use to_char().
My work around was to select it from the final select, ie

with cte as (
    select
        mytable1.myIntCol
    from mytable1
)
select myIntCol, myClobCol
from cte
join mytable2 on ...
where ...

Too bad if this causes a performance problem.

The same error occurs also when doing SELECT DISTINCT ..., <CLOB_column>, ....

If this CLOB column contains values shorter than limit for VARCHAR2 in all the applicable rows you may use to_char(<CLOB_column>) or concatenate results of multiple calls to DBMS_LOB.SUBSTR(<CLOB_column>, ...).

Take a substr of the CLOB and then convert it to a char:

UPDATE IMS_TEST 
  SET TEST_Category           = 'just testing' 
WHERE to_char(substr(TEST_SCRIPT, 1, 9))    = 'something'
  AND ID                      = '10000239';

I just ran over this one and I found by accident that CLOBs can be used in a like query:

   UPDATE IMS_TEST 
   SET TEST_Category  = 'just testing'  
 WHERE TEST_SCRIPT    LIKE '%something%'
   AND ID             = '10000239' 

This worked also for CLOBs greater than 4K

The Performance won't be great but that was no problem in my case.

The problem may lie in selected null values ??in combination with a CLOB-type column.

select valueVarchar c1 ,
       valueClob c2 ,
       valueVarchar c3 ,
       valueVvarchar c4
of Table_1
union
select valueVarchar c1 ,
       valueClob c2 ,
       valueVarchar c3 ,
       null c4
of table_2

I reworked the cursor. The first cursor is composed of four non-null columns. The second cursor selects three non-null columns. The null values ??were injected into the cursorForLoop .