【Oracle Database】数据库约束管理

主键约束
SQL> alter table customers add constraint customers_pk primary key (customer_id);  
Table altered.

col constraint_name for a30
col constraint_type for a15
col table_name for a30
col index_name for a30

SQL> select constraint_name,constraint_type,table_name,index_name,status from dba_constraints where constraint_type = ‘P‘ and owner = ‘SOE‘;
CONSTRAINT_NAME                CONSTRAINT_TYPE TABLE_NAME                     INDEX_NAME                     STATUS
------------------------------ --------------- ------------------------------ ------------------------------ --------
CUSTOMERS_PK                   P               CUSTOMERS                      CUSTOMERS_PK                   ENABLED

col constraint_name for a30
col constraint_type for a15
col table_name for a30
col column_name for a30

SQL> select dba_cons_columns.constraint_name,
dba_cons_columns.table_name,
dba_cons_columns.column_name,
dba_cons_columns.position
from dba_constraints join dba_cons_columns
on (dba_constraints.constraint_name = dba_cons_columns.constraint_name)
where constraint_type = ‘P‘ and dba_constraints.owner = ‘SOE‘;
CONSTRAINT_NAME                TABLE_NAME                     COLUMN_NAME                      POSITION
------------------------------ ------------------------------ ------------------------------ ----------
CUSTOMERS_PK                   CUSTOMERS                      CUSTOMER_ID                             1

禁用约束
SQL> alter table customers disable constraint customers_pk;

启用约束
SQL> alter table customers enable constraint customers_pk;

删除约束
SQL> alter table customers drop constraint customers_pk;

外键约束
SQL> alter table orders add constraint orders_customer_id_fk foreign key (customer_id) references customers (customer_id);
Table altered.

col constraint_name for a30
col constraint_type for a20
col table_name for a20
col r_constraint_name for a30
col delete_rule for a15

SQL> select constraint_name,constraint_type,table_name,r_constraint_name,delete_rule,status from dba_constraints where constraint_type = ‘R‘ and owner = ‘SOE‘;
CONSTRAINT_NAME                CONSTRAINT_TYPE      TABLE_NAME           R_CONSTRAINT_NAME              DELETE_RULE     STATUS
------------------------------ -------------------- -------------------- ------------------------------ --------------- --------
ORDERS_CUSTOMER_ID_FK          R                    ORDERS               CUSTOMERS_PK                   NO ACTION       ENABLED

col child_table_name for a20
col father_table_name for a20
col child_column_name for a20
col father_column_name for a20

SQL> select dba_cons_columns.constraint_name,
dba_cons_columns.table_name as child_table_name,
dba_cons_columns.column_name as child_column_name,
dba_cons_columns.position,
dba_indexes.table_name as father_table_name,
dba_ind_columns.column_name as father_column_name
from
dba_constraints join dba_cons_columns on (dba_constraints.constraint_name = dba_cons_columns.constraint_name)
join dba_indexes on (dba_constraints.r_constraint_name = dba_indexes.index_name)
join dba_ind_columns on (dba_indexes.index_name = dba_ind_columns.index_name) where constraint_type =‘R‘ and dba_constraints.owner = ‘SOE‘;
CONSTRAINT_NAME                CHILD_TABLE_NAME     CHILD_COLUMN_NAME      POSITION FATHER_TABLE_NAME    FATHER_COLUMN_NAME
------------------------------ -------------------- -------------------- ---------- -------------------- --------------------
ORDERS_CUSTOMER_ID_FK          ORDERS               CUSTOMER_ID                   1 CUSTOMERS            CUSTOMER_ID

1、普通外键约束（如果存在子表引用父表主键，则无法删除父表记录）
SQL> alter table orders add constraint orders_customer_id_fk foreign key (customer_id) references customers (customer_id);
2、级联外键约束（可删除存在引用的父表记录，而且同时把所有有引用的子表记录也删除）
SQL> alter table orders add constraint orders_customer_id_fk foreign key (customer_id) references customers (customer_id) on delete cascade;
3、置空外键约束（可删除存在引用的父表记录，同时将子表中引用该父表主键的外键字段自动设为NULL，但该字段应允许空值）
SQL> alter table orders add constraint orders_customer_id_fk foreign key (customer_id) references customers (customer_id) on delete set null;