postgresql----根据现有表创建新表

除普通的建表语句"create table table_name(columns);"之外，还可以根据现有表快速的创建新表:

一.使用create table ... (like ...)创建一个和原表结构相同的新表，根据INCLUDING保留原表的约束，索引等。

create table table_name (like parent_table {INCLUDING|EXCLUDING}{DEFAULTS|CONSTRAINTS|INDEXES|STORAGE|COMMENTS|ALL});

直接使用LIKE不使用INCLUDING，新表只保留原表的表结构和NOT NULL约束，但是使用INCLUDING CONSTRAINTS配置会保留了主键，唯一键，CHECK约束，并不会保留外键约束。

示例：

1.创建示例表

test=# create table tbl_inherits_test (a int not null);
CREATE TABLE
test=# alter table tbl_inherits_test add constraint pk_tbl_inherits_test_a primary key(a);
ALTER TABLEtest=# create table tbl_inherits_parent(
 a int not null,
 b varchar(32) not null default ‘got u‘,
 c int,
 d date);

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 fk_tbl_inherits_parent_a foreign key(a) references tbl_inherits_test(a);
ALTER TABLE
test=# alter table tbl_inherits_parent add constraint ck_tbl_inherits_parent_c check (c>10);
ALTER TABLE
test=# alter table tbl_inherits_parent add constraint uk_tbl_inherits_parent_b_d unique (b,d);
ALTER TABLE

test=# create index idx_tbl_inherits_parent_d on tbl_inherits_parent using btree (d);
  CREATE INDEX

2.使用LIKE创建表

test=# create table tbl_inherits_partition (like tbl_inherits_parent including constraints including indexes including defaults);
CREATE TABLE

test=# \d tbl_inherits_parent
                      Table "public.tbl_inherits_parent"
 Column |         Type          |                  Modifiers
--------+-----------------------+---------------------------------------------
 a      | integer               | not null
 b      | character varying(32) | not null default ‘got u‘::character varying
 c      | integer               |
 d      | date                  |
Indexes:
    "pk_tbl_inherits_parent_a" PRIMARY KEY, btree (a)
    "uk_tbl_inherits_parent_b_d" UNIQUE CONSTRAINT, btree (b, d)
    "idx_tbl_inherits_parent_d" btree (d)
Check constraints:
    "ck_tbl_inherits_parent_c" CHECK (c > 10)
Foreign-key constraints:
    "fk_tbl_inherits_parent_a" FOREIGN KEY (a) REFERENCES tbl_inherits_test(a)

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                  |
Indexes:
    "tbl_inherits_partition_pkey" PRIMARY KEY, btree (a)
    "tbl_inherits_partition_b_d_key" UNIQUE CONSTRAINT, btree (b, d)
    "tbl_inherits_partition_d_idx" btree (d)
Check constraints:
    "ck_tbl_inherits_parent_c" CHECK (c > 10)

二、使用create table ... as table ... with {data|no data}创建一个和原表结构相同的新表，保留或不保留数据，但是不会继承原表的约束，索引等。

test=# insert into tbl_inherits_test values (1);
INSERT 0 1
test=# insert into tbl_inherits_parent (a,b,c,d) values(1,‘sss‘,12,‘2016-06-22 17:00:00‘);
INSERT 0 1
test=#
test=# create table tbl_inherits_partition1 as table tbl_inherits_parent with data;
SELECT 1
test=# select * from tbl_inherits_partition1 ;
 a |  b  | c  |     d
---+-----+----+------------
 1 | sss | 12 | 2016-06-22
(1 row)

test=# \d tbl_inherits_partition1
   Table "public.tbl_inherits_partition1"
 Column |         Type          | Modifiers
--------+-----------------------+-----------
 a      | integer               |
 b      | character varying(32) |
 c      | integer               |
 d      | date                  | 

test=#
test=#
test=# create table tbl_inherits_partition2 as table tbl_inherits_parent with no data;
SELECT 0
test=# \d tbl_inherits_partition2
   Table "public.tbl_inherits_partition2"
 Column |         Type          | Modifiers
--------+-----------------------+-----------
 a      | integer               |
 b      | character varying(32) |
 c      | integer               |
 d      | date                  | 

test=# select * from tbl_inherits_partition2;
 a | b | c | d
---+---+---+---
(0 rows)

test=# 

三、使用select * into new_table from table将结果集保存在新表中，但是只能执行一次。

test=# select * into tbl_inherits_partition3 from tbl_inherits_parent ;
SELECT 1
test=# \d tbl_inherits_partition3
   Table "public.tbl_inherits_partition3"
 Column |         Type          | Modifiers
--------+-----------------------+-----------
 a      | integer               |
 b      | character varying(32) |
 c      | integer               |
 d      | date                  | 

test=# select * from tbl_inherits_partition3 ;
 a |  b  | c  |     d
---+-----+----+------------
 1 | sss | 12 | 2016-06-22
(1 row)

四、使用create table new_table as select * from table将结果集保存在新表中。

test=# create table tbl_inherits_partition4 as select * from tbl_inherits_parent ;
SELECT 1
test=# \d tbl_inherits_partition4
   Table "public.tbl_inherits_partition4"
 Column |         Type          | Modifiers
--------+-----------------------+-----------
 a      | integer               |
 b      | character varying(32) |
 c      | integer               |
 d      | date                  | 

test=# select * from tbl_inherits_partition4 ;
 a |  b  | c  |     d
---+-----+----+------------
 1 | sss | 12 | 2016-06-22
(1 row)