While truncating a table in database, might face the error ORA-02266 unique key error.

PROBLEM:

SQL> truncate table DBACLASS.AAF_USER;
truncate table DBACLASS.AAF_USER
*
ERROR at line 1:
ORA-02266: unique/primary keys in table referenced by enabled foreign keys

SOLUTION:

The primary key in the table( which we are truncating) , seems to be referring to a another child table with foreign key.

Run below script to get the parent table , child table relation

set lines 2999
COL CHILD_TABLE FOR A20
col CONSTRAINT_NAME for a26
col owner form a10
col FK_column form a15
col table_name form a30
select b.owner, b.table_name child_table,
c.column_name FK_column, b.constraint_name
from dba_constraints a, dba_constraints b, dba_cons_columns c
where a.owner=b.r_owner
and b.owner=c.owner
and b.table_name=c.table_name
and b.constraint_name=c.constraint_name
and a.constraint_name=b.r_constraint_name
and b.constraint_type='R'
and a.owner='&owner'
and a.table_name='&TABLE_NAME'
and a.CONSTRAINT_TYPE='P';

OWNER      CHILD_TABLE          FK_COLUMN       CONSTRAINT_NAME
---------- -------------------- --------------- --------------------------
DBACLASS   AAF_USER_MEMBER      MEMBER          AAF_USER_FK1

So either disable or drop this foreign constraint and try to truncate.

SQL> alter table dbaclass.AAF_USER_MEMBER disable constraint AAF_USER_FK1;

Table altered.

SQL> truncate table dbaclass.AAF_USER;

Table truncated.