LONG column and translate function

Question

I want to get the default values of columns through all_tab_columns.
I have written the query :
select a.COLUMN_NAME, translate(a.DATA_DEFAULT,'''',' ')
from all_tab_columns a
where a.TABLE_NAME like 'T_MPR_MBT'
But it gives the following error:
ORA-00932: inconsistent datatypes: expected NUMBER got LONG
Is there a way to convert long to string?
Thanks
Ameya.

Answer 1

SQL> describe long_tab;
Name                                                                          Null?    Type
COL1                                                                                   NUMBER
COL2                                                                                   LONG
COL3                                                                                   VARCHAR2(40)
SQL> select * from long_tab;
      COL1 COL2                                                                             COL3
         1 1st value for long characters                                                    1st value for long characters
         2
         3 3rd value for long characters                                                    3rd value for long characters
SQL> select * from long_tab
  2   where nvl(col2,'x') = nvl(col2,'x');
where nvl(col2,'x') = nvl(col2,'x')
ERROR at line 2:
ORA-00932: inconsistent datatypes: expected LONG got CHAR
-- we know that we cannot compare a column with long datatype to other column that is not a long datatype.
-- we have to create some custom function to convert the long into a character type.
SQL> CREATE OR REPLACE Function convert_long_to_char( pTableName in varchar2,
  2                                                   pColumnName in varchar2,
  3                                                   pRowId in rowid ) return varchar2 As
  4    vCursor    integer default dbms_sql.open_cursor;
  5    vN         number;
  6    vLongVal  varchar2(4000);
  7    vLongLen  number;
  8    vBuflen    number := 4000;
  9    vCurPos    number := 0;
10  begin
11    dbms_sql.parse( vCursor,'select ' || pColumnName || ' from ' || pTableName ||
12                                                            ' where rowid = :x',
13                    dbms_sql.native );
14    dbms_sql.bind_variable( vCursor, ':x', pRowId );
15 
16    dbms_sql.define_column_long(vCursor, 1);
17    vN := dbms_sql.execute(vCursor);
18 
19    if (dbms_sql.fetch_rows(vCursor)>0) then
20      dbms_sql.column_value_long(vCursor, 1, vBuflen, vCurpos ,
21                                 vLongVal, vLongLen );
22    end if;
23    dbms_sql.close_cursor(vCursor);
24    return vLongVal;
25  end convert_long_to_char;
26  /
Function created.
SQL> select * from long_tab
  2   where nvl(convert_long_to_char('long_tab','col2',rowid),'x') = nvl(col3,'x');
      COL1 COL2                                                                             COL3
         1 1st value for long characters                                                    1st value for long characters
         2
         3 3rd value for long characters                                                    3rd value for long characters
SQL>
-- in your case it would something like:
select a.COLUMN_NAME,
       translate(convert_long_to_char('all_tab_columns','DATA_DEFAULT',rowid),'''',' ')
  from all_tab_columns a
  where a.TABLE_NAME like 'T_MPR_MBT';