Oracle 檢視一個表對應的主鍵和外來鍵的約束關係，檢視的語句：

select a.owner 主鍵擁有者

         ,a.table_name 主鍵表

        ,b.column_name 主鍵列

        ,C.OWNER 外來鍵擁有者

        ,c.table_name 外來鍵表

       ,d.column_name 外來鍵列
from user_constraints a
left join user_cons_columns b

            on a.constraint_name=b.constraint_name
left join user_constraints C

            ON C.R_CONSTRAINT_NAME=a.constraint_name
left join user_cons_columns d

            on c.constraint_name=d.constraint_name
where a.constraint_type='P'

    and a.table_name='XXX' --需要檢視主外來鍵關係的表
order by a.table_name

寧外的一種寫法

select
a.owner 外來鍵擁有者,
a.table_name 外來鍵表,
substr(c.column_name,1,127) 外來鍵列,
b.owner 主鍵擁有者,
b.table_name 主鍵表,
substr(d.column_name,1,127) 主鍵列
from
user_constraints a,
user_constraints b,
user_cons_columns c,
user_cons_columns d
where
    a.r_constraint_name=b.constraint_name
and a.constraint_type='R'
and b.constraint_type='P'
and a.r_owner=b.owner
and a.constraint_name=c.constraint_name
and b.constraint_name=d.constraint_name
and a.owner=c.owner
and a.table_name=c.table_name
and b.owner=d.owner
and b.table_name=d.table_name

資料字典表列說明：

desc user_constraints

Name Comments
OWNER 表的所有者
CONSTRAINT_NAME 約束名
CONSTRAINT_TYPE 約束型別
TABLE_NAME Name associated with table with constraint definition
SEARCH_CONDITION Text of search condition for table check
R_OWNER Owner of table used in referential constraint
R_CONSTRAINT_NAME Name of unique constraint definition for referenced table
DELETE_RULE The delete rule for a referential constraint
STATUS Enforcement status of constraint - ENABLED or DISABLED
DEFERRABLE Is the constraint deferrable - DEFERRABLE or NOT DEFERRABLE
DEFERRED Is the constraint deferred by default - DEFERRED or IMMEDIATE
VALIDATED Was this constraint system validated? - VALIDATED or NOT VALIDATED
GENERATED Was the constraint name system generated? - GENERATED NAME or USERNAME
BAD Creating this constraint should give ORA-02436. Rewrite it before2000 AD.
RELY If set, this flag will be used in optimizer
LAST_CHANGE The date when this column was last enabled or disabled
INDEX_OWNER The owner of the index used by the constraint
INDEX_NAME The index used by the constraint
INVALID  
VIEW_RELATED  

desc user_cons_columns;

Name Default Comments
OWNER Owner of the constraint definition
CONSTRAINT_NAME Name associated with the constraint definition
TABLE_NAME Name associated with table with constraint definition
COLUMN_NAME Name associated with column or attribute of object column specified in the constraint definition
POSITION Original position of column or attribute in definition

desc   後發現
user_constraints是表約束的檢視,描述的是約束型別(constraint_type)是什麼,屬於哪些表(table_name),如 果約束的型別為R(外來鍵)的話,那麼r_constraint_name欄位存放的就是被引用主表中的主鍵約束名。   
user_cons_columns是表約束欄位的檢視,說明表中的和約束相關的列參與了哪些約束。這些約束有主鍵約束,外來鍵約束,索引約束.
兩者可以通過(owner,constraint_name,table_name)關聯

select
a.owner 外來鍵擁有者,
a.table_name 外來鍵表,
substr(c.column_name,1,127) 外來鍵列,
b.owner 主鍵擁有者,
b.table_name 主鍵表,
substr(d.column_name,1,127) 主鍵列
from
user_constraints a,
user_constraints b,
user_cons_columns c,
user_cons_columns d
where
    a.r_constraint_name=b.constraint_name
and a.constraint_type='R'
and b.constraint_type='P'
and a.r_owner=b.owner
and a.constraint_name=c.constraint_name
and b.constraint_name=d.constraint_name
and a.owner=c.owner
and a.table_name=c.table_name
and b.owner=d.owner
and b.table_name=d.table_name

資料字典表列說明：

desc user_constraints

Name                                      

/////////////////////////////////////

Oracle 檢視一個表對應的主鍵和外來鍵的約束關係，檢視的語句：

select a.owner 主鍵擁有者

         ,a.table_name 主鍵表

        ,b.column_name 主鍵列

        ,C.OWNER 外來鍵擁有者

        ,c.table_name 外來鍵表

       ,d.column_name 外來鍵列
from user_constraints  a
left join user_cons_columns b

            on  a.constraint_name=b.constraint_name
left join user_constraints C

            ON C.R_CONSTRAINT_NAME=a.constraint_name
left join user_cons_columns d

            on c.constraint_name=d.constraint_name
where  a.constraint_type='P'

    and  a.table_name='XXX' --需要檢視主外來鍵關係的表
order by a.table_name

寧外的一種寫法

select
a.owner 外來鍵擁有者,
a.table_name 外來鍵表,
substr(c.column_name,1,127) 外來鍵列,
b.owner 主鍵擁有者,
b.table_name 主鍵表,
substr(d.column_name,1,127) 主鍵列
from
user_constraints a,
user_constraints b,
user_cons_columns c,
user_cons_columns d
where
    a.r_constraint_name=b.constraint_name
and a.constraint_type='R'
and b.constraint_type='P'
and a.r_owner=b.owner
and a.constraint_name=c.constraint_name
and b.constraint_name=d.constraint_name
and a.owner=c.owner
and a.table_name=c.table_name
and b.owner=d.owner
and b.table_name=d.table_name

資料字典表列說明：

desc user_constraints

desc user_cons_columns;