Create a relation that represents the dependence between objects. The table shou

Question

Create a relation that represents the dependence between objects. The table should have two attributes called object and dependent, where object is the primary key of the relation and dependent is a foreign key that references object. Then insert three tuples into this table:

1. o1 is dependent on o2

2. o2 is dependent on o3

3. o3 is dependent on o1

Note that this problem is similar to chicken-egg problem but only involves one relation. What you need to submit is proper DDL and DML statements in sequence that can accomplish this with Oracle-VM.

Explanation / Answer

Hi,

Below are the DDL and DML statement. DDL create table will execute successfully but DML will not execute.

The reason is because of below reasons-

1. o1 is dependent on o2 - We are trying to insert the dependent o2 here which does not exist in the object column.

As a result, we get the integrity constraint violation error-

ORA-02291: integrity constraint (SQL_QCIWFJAKILUMKJVCAOCLUGLQZ.SYS_C006921033) violated - parent key not found ORA-06512: at "SYS.DBMS_SQL", line 1721

2. o2 is dependent on o3 - We are trying to insert the dependent o3 here which does not exist in the object column.

As a result, we get the integrity constraint violation error

3. o3 is dependent on o1 - We are trying to insert the dependent o1 here which does not exist in the object column.

As a result, we get the integrity constraint violation error

DDL Statements-

CREATE TABLE TEST(OBJECT VARCHAR(20) PRIMARY KEY, DEPENDENT VARCHAR(20) REFERENCES TEST(OBJECT));

INSERT INTO TEST VALUES('o1','o2');
INSERT INTO TEST VALUES('o2','o3');
INSERT INTO TEST VALUES('o3','o1');

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