postgresql----继承表inherits parent table

使用INHERITS创建的新表会继承一个或多个父表，子表只会继承父表的表结构和NOT NULL，DEFAULT，CHECK三种约束，主键，外键和唯一键以及索引不会被继承，所以修改父表的结构（增删字段），NOT NULL，DEFAULT和CHECK约束会自动同步子表修改。

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.

除继承父表之外，创建子表时可以增加自己的字段

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.解除继承

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)