Question

I’m trying to delete all foreign keys of a table. First I get all the names of those keys using meta.getExportedKeys(null, null, table); and rs.getString("FK_NAME").

But when I try to delete this key using:

ALTER TABLE tablename DROP CONSTRAINT fkname

it only works for some keys. Sometimes I’m getting:

ORA-02443: Cannot drop constraint - nonexistent constraint

But the foreign key is definitely there. What am I doing wrong?

Answer 1

Have you tried

ALTER TABLE tablename DROP CONSTRAINT "fkname";

instead?

You might have created the constraint in a case-sensitive way, in which case, you’ll need to put the constraint name in double quotes when you drop it. Here’s an example session in SQL*Plus:

SQL> create table test (a integer);

Table created.

SQL> alter table test add constraint "abcd" unique (a);

Table altered.

SQL> alter table test drop constraint abcd;
alter table test drop constraint abcd
                                 *
ERROR at line 1:
ORA-02443: Cannot drop constraint  - nonexistent constraint


SQL> alter table test drop constraint "abcd";

Table altered.

SQL>