oracle 查看主外键约束

select a.constraint_name, a.table_name, b.constraint_name

from user_constraints a, user_constraints b

where a.constraint_type = 'R'

and b.constraint_type = 'P'

and a.r_constraint_name = b.constraint_name

P 代表主键

R 代表外键

通过关联，能查询到你所想要的一切。



select constraint_name from dba_cons_columns where table_name='';

Alter table XX drop constraint sys…

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user_constraints,user_cons_columns查看外键

Oracle 查看一个表对应的主键和外键的约束关系，查看的语句：

select a.owner 主键拥有者

,a.table_name 主键表

,b.column_name 主键列

,C.OWNER 外键拥有者

,c.table_name 外键表

,d.column_name 外键列

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' --需要查看主外键关系的表

order by a.table_name

宁外的一种写法

select

a.owner 外键拥有者,

a.table_name 外键表,

substr(c.column_name,1,127) 外键列,

b.owner 主键拥有者,

b.table_name 主键表,

substr(d.column_name,1,127) 主键列

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

数据字典表列说明：

desc user_constraints

Name Comments

OWNER 表的所有者

CONSTRAINT_NAME 约束名

CONSTRAINT_TYPE 约束类型

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



http://blog.csdn.net/maqinqin/archive/2009/05/26/4217045.aspx

desc 后发现

user_constraints是表约束的视图,描述的是约束类型(constraint_type)是什么,属于哪些表(table_name),如
果约束的类型为R(外键)的话,那么r_constraint_name字段存放的就是被引用主表中的主键约束名。

user_cons_columns是表约束字段的视图,说明表中的和约束相关的列参与了哪些约束。这些约束有主键约束,外键约束,索引约束.

两者可以通过(owner,constraint_name,table_name)关联

select

a.owner 外键拥有者,

a.table_name 外键表,

substr(c.column_name,1,127) 外键列,

b.owner 主键拥有者,

b.table_name 主键表,

substr(d.column_name,1,127) 主键列

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

数据字典表列说明：

desc user_constraints

Name

http://www.blogjava.net/sunzhong/articles/289139.html



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Oracle 查看一个表对应的主键和外键的约束关系，查看的语句：

select a.owner 主键拥有者

,a.table_name 主键表

,b.column_name 主键列

,C.OWNER 外键拥有者

,c.table_name 外键表

,d.column_name 外键列

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' --需要查看主外键关系的表

order by a.table_name

宁外的一种写法

select

a.owner 外键拥有者,

a.table_name 外键表,

substr(c.column_name,1,127) 外键列,

b.owner 主键拥有者,

b.table_name 主键表,

substr(d.column_name,1,127) 主键列

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

数据字典表列说明：

desc user_constraints

Name	Comments
OWNER	表的所有者
CONSTRAINT_NAME	约束名
CONSTRAINT_TYPE	约束类型
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