Oracle Data Pump imported table, some columns not selectable

Question

Imported a table into Oracle 12g using data pump. Some of the columns, though present in the table as shown by describe, cannot be selected but they show up in select *.

Cannot select them individually or apply where clause on only these columns.

Answer 1

Let me guess: when you describe the table, you see lowercase letters in column names, meaning the column name is case-sensitive, but you tried to select it without double quotes, in a case-insensitive manner.

Try quotes as in the below example:

SQL> create table t1(column1 number, "column2" number);

Table created.

SQL> insert into t1 values (1, 1);

1 row created.

SQL> commit;

Commit complete.

SQL> desc t1
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 COLUMN1                                            NUMBER
 column2                                            NUMBER

SQL> select COLUMN1, column2 from t1;
select COLUMN1, column2 from t1
                *
ERROR at line 1:
ORA-00904: "COLUMN2": invalid identifier


SQL> select * from t1;

   COLUMN1    column2
---------- ----------
         1          1

SQL> select COLUMN1, "column2" from t1;

   COLUMN1    column2
---------- ----------
         1          1