How to Remove Foreign Key Constraint

Question

Hello Freinds,
I have created two sample tables ...
create table primaryTable(id int primary key,value int);
OK; 1 row affected
create table childTable(id1 int primary key,id int references primaryTable(id),value int);
OK; 1 row affected
ants_dsn_3.4> select * from childTable;
| ID1 | ID | VALUE |
| 1 | 1 | 1 |
| 2 | 2 | 1 |
| 3 | 3 | 1 |
OK; Returned 3 rows from 3 fields
ants_dsn_3.4> select * from primaryTable;
--------------------------+
| ID | VALUE |
--------------------------+
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
--------------------------+
I want to drop the Foreign key in the Child Table.
And when i do that i get the Following error.
ants_dsn_3.4> alter table childTable drop ID;
[ANTs Software][ANTs DATABASE ODBC driver][ants_dsn_3.4] Server returned error : ERROR (70007): Cannot drop the column 'ID' that has a constraint on it
Freinds Can you help to solve this problem as iam new to data base side.
Thanks in advance,
Faizan.

Answer 1

The reason you are having a problem is that you are using a very bad technique for creating your constraints.
SQL> create table primaryTable(id int primary key,value int);
Table created.
SQL> create table childTable(id1 int primary key,id int references primaryTable(id),value int);
Table created.
SQL> select constraint_name, constraint_type
  2  from user_constraints
  3  where table_name = 'CHILDTABLE';
CONSTRAINT_NAME                C
SYS_C0011508                   P
SYS_C0011509                   R
SQL> ALTER TABLE childtable DROP CONSTRAINT SYS_C0011509;
Table altered.
SQL> Create your constraints properly and you won't get system generated names.
CREATE TABLE primaryTable(id INTEGER, value INTEGER);
ALTER TABLE primarytable
ADD CONSTRAINT pk_primarytable
PRIMARY KEY (id)
USING INDEX;And columns named ID and VALUE are enough to make me refuse to hire someone for a job. Get a copy of Joe Celko's books and learn how to name columns. Also do not use reserved words for column names:
SELECT keyword
FROM gv$reserved_words;Now lets get back to your referential constraint:
CREATE TABLE childTable(id1 INTEGER, id INTEGER, value INTEGER);
ALTER TABLE childtable
ADD CONSTRAINT pk_childtable
PRIMARY KEY (id)
USING INDEX;
ALTER TABLE childtable
ADD CONSTRAINT fk_child_primary_id
FOREIGN KEY (id)
REFERENCING primarytable(id);BTW: I would fail a first quarter student who, on their midterm, wrote what you've written above. You should find yourself a good beginning book on database design.