postgresql----繼承表INHERITS PARENT TABLE

 

使用INHERITS建立的新表會繼承一個或多個父表，子表只會繼承父表的表結構和NOT NULL，DEFAULT，CHECK三種約束，主鍵，外鍵和惟一鍵以及索引不會被繼承，因此修改父表的結構（增刪字段），NOT NULL，DEFAULT和CHECK約束會自動同步子表修改。

示例1.

create table tbl_inherits_parent(
a int not null,
b varchar(32) not null default 'Got u',
c int check (c > 0),
d date not null
);

test=# alter table tbl_inherits_parent add constraint pk_tbl_inherits_parent_a primary key(a);
ALTER TABLE

test=# alter table tbl_inherits_parent add constraint uk_tbl_inherits_parent_b_d unique (b,d);
ALTER TABLE

test=# create table tbl_inherits_partition() inherits (tbl_inherits_parent);
CREATE TABLE
test=# \d tbl_inherits_partition 
                    Table "public.tbl_inherits_partition"
 Column |         Type          |                  Modifiers                  
--------+-----------------------+---------------------------------------------
 a      | integer               | not null
 b      | character varying(32) | not null default 'Got u'::character varying
 c      | integer               | 
 d      | date                  | not null
Check constraints:
    "tbl_inherits_parent_c_check" CHECK (c > 0)
Inherits: tbl_inherits_parent

 

示例2.

test=# alter table tbl_inherits_parent add column e int not null default 0;
ALTER TABLE
test=# alter table tbl_inherits_parent alter column b set default 'try me';
ALTER TABLE
test=# \d tbl_inherits_partition 
                     Table "public.tbl_inherits_partition"
 Column |         Type          |                  Modifiers                   
--------+-----------------------+----------------------------------------------
 a      | integer               | not null
 b      | character varying(32) | not null default 'try me'::character varying
 c      | integer               | 
 d      | date                  | not null
 e      | integer               | not null default 0
Check constraints:
    "tbl_inherits_parent_c_check" CHECK (c > 0)
Inherits: tbl_inherits_parent

 

示例3.

除繼承父表以外，建立子表時能夠增長本身的字段

test=# create table tbl_inherits_partition1(f int) inherits (tbl_inherits_parent);
CREATE TABLE
test=# \d tbl_inherits_partition1 
                    Table "public.tbl_inherits_partition1"
 Column |         Type          |                  Modifiers                   
--------+-----------------------+----------------------------------------------
 a      | integer               | not null
 b      | character varying(32) | not null default 'try me'::character varying
 c      | integer               | 
 d      | date                  | not null
 e      | integer               | not null default 0
 f      | integer               | 
Check constraints:
    "tbl_inherits_parent_c_check" CHECK (c > 0)
Inherits: tbl_inherits_parent

 

示例4.解除繼承

test=# alter table tbl_inherits_partition1 no inherit tbl_inherits_parent;
ALTER TABLE
test=# \d tbl_inherits_partition1 
                    Table "public.tbl_inherits_partition1"
 Column |         Type          |                  Modifiers                   
--------+-----------------------+----------------------------------------------
 a      | integer               | not null
 b      | character varying(32) | not null default 'try me'::character varying
 c      | integer               | 
 d      | date                  | not null
 e      | integer               | not null default 0
 f      | integer               | 
Check constraints:
    "tbl_inherits_parent_c_check" CHECK (c > 0)