truncate清空一张表记录发现ORA-02266，进行模拟测试

SQL> truncate table p;
truncate table p
               *
ERROR at line 1:
ORA-02266: unique/primary keys in table referenced by enabled foreign keys
--错误原因
SQL> !oerr ora 02266
02266, 00000, "unique/primary keys in table referenced by enabled foreign keys"
// *Cause: An attempt was made to truncate a table with unique or
//         primary keys referenced by foreign keys enabled in another table.
//         Other operations not allowed are dropping/truncating a partition of a
//         partitioned table or an ALTER TABLE EXCHANGE PARTITION.
// *Action: Before performing the above operations the table, disable the
//          foreign key constraints in other tables. You can see what
//          constraints are referencing a table by issuing the following
//          command:
//          SELECT * FROM USER_CONSTRAINTS WHERE TABLE_NAME = "tabnam";
--查询是否有主键或者唯一index
SET SERVEROUTPUT ON
SET LINESIZE 1000
SET FEEDBACK OFF
SET LONG 999999
SET PAGESIZE 1000
EXEC DBMS_METADATA.SET_TRANSFORM_PARAM(DBMS_METADATA.SESSION_TRANSFORM,'STORAGE',false);--不显示存储信息
SQL> SELECT DBMS_METADATA.GET_DDL('TABLE','P') FROM DUAL;
DBMS_METADATA.GET_DDL('TABLE','P')
--------------------------------------------------------------------------------
  CREATE TABLE "CHF"."P"
   (    "X" NUMBER(*,0),
         PRIMARY KEY ("X")
  USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255
  TABLESPACE "USERS"  ENABLE
   ) PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING
  TABLESPACE "USERS
--查询主外键关系
SQL> col 主键表名 for a20
SQL> col 主键列名 for a20
SQL> col 外键表名 for a20
SQL> col 外键列名  for a20
SQL> select b.table_name  主键表名,
       b.column_name 主键列名,
       a.table_name  外键表名,
       a.column_name 外键列名
  from (select a.constraint_name,
               b.table_name,
               b.column_name,
               a.r_constraint_name
          from dba_constraints a, dba_cons_columns b
         WHERE a.constraint_type = 'R'
           and a.constraint_name = b.constraint_name) a,
       (select distinct a.r_constraint_name, b.table_name, b.column_name
          from dba_constraints a, dba_cons_columns b
         WHERE a.constraint_type = 'R'
           and a.r_constraint_name = b.constraint_name) b
 where a.r_constraint_name = b.r_constraint_name
and b.table_name='P';
主键表名             主键列名             外键表名             外键列名
-------------------- -------------------- -------------------- --------------------
P                    X                    C                    X
1 row selected.
--处理方法一
SQL> alter table p disable primary key cascade;
Table altered.
SQL> truncate table p;
Table truncated.
SQL> alter table p enable primary key;
Table altered.
--处理方法二
SQL> delete from t;
1 row deleted.
SQL> commit;
Commit complete.