PostgreSQL数组使用(转载)

 

开发的语言有数组的概念，对应于postgresql也有相关的数据字段类型，数组是英文array的翻译，可以定义一维，二维甚至更多维度，数学上跟矩阵很类似。在postgres里面可以直接存储使用，某些场景下使用很方便，也很强大。

环境：
OS：CentOS 6.2
DB: PostgreSQL 9.2.4

1.数组的定义
不一样的维度元素长度定义在数据库中的实际存储都是一样的，数组元素的长度和类型必须要保持一致，并且以中括号来表示。
合理的：
array[1,2]            --一维数组
array[[1,2],[3,5]]  --二维数组
'{99,889}'

不合理的:
array[[1,2],[3]]                     --元素长度不一致
array[[1,2],['Kenyon','good']]  --类型不匹配

[postgres@localhost ~]$ psql
psql (9.2.4)
Type "help" for help.
postgres=# create table t_kenyon(id serial primary key,items int[]);
NOTICE:  CREATE TABLE will create implicit sequence "t_kenyon_id_seq" for serial column "t_kenyon.id"
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t_kenyon_pkey" for table "t_kenyon"
CREATE TABLE
postgres=# \d+ t_kenyon
                                              Table "public.t_kenyon"
Column |   Type    |                       Modifiers                       | Storage  | Stats target | Description
--------+-----------+-------------------------------------------------------+----------+--------------+-------------
id     | integer   | not null default nextval('t_kenyon_id_seq'::regclass) | plain    |              |
items  | integer[] |                                                       | extended |              |
Indexes:
    "t_kenyon_pkey" PRIMARY KEY, btree (id)
Has OIDs: no

postgres=# create table t_ken(id serial primary key,items int[4]);
NOTICE:  CREATE TABLE will create implicit sequence "t_ken_id_seq" for serial column "t_ken.id"
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "t_ken_pkey" for table "t_ken"
CREATE TABLE

postgres=# \d+ t_ken
                                              Table "public.t_ken"
 Column |   Type    |                     Modifiers                      | Storage  | Stats target | Description 
--------+-----------+----------------------------------------------------+----------+--------------+-------------
 id     | integer   | not null default nextval('t_ken_id_seq'::regclass) | plain    |              | 
 items  | integer[] |                                                    | extended |              | 
Indexes:
    "t_ken_pkey" PRIMARY KEY, btree (id)
Has OIDs: no

数组的存储方式是extended的。

2.数组操作

a.数据插入，有两种方式
postgres=# insert into t_kenyon(items) values('{1,2}');
INSERT 0 1
postgres=# insert into t_kenyon(items) values('{3,4,5}');
INSERT 0 1
postgres=# insert into t_kenyon(items) values(array[6,7,8,9]);
INSERT 0 1
postgres=# select * from t_kenyon;
id |   items  
----+-----------
  1 | {1,2}
  2 | {3,4,5}
  3 | {6,7,8,9}
(3 rows)

b.数据删除

postgres=# delete from t_kenyon where id = 3;
DELETE 1
postgres=# delete from t_kenyon where items[1] = 4;
DELETE 0
postgres=# delete from t_kenyon where items[1] = 3;
DELETE 1

c.数据更新

往后追加
postgres=# update t_kenyon set items = items||7;
UPDATE 1
postgres=# select * from t_kenyon;
id |  items 
----+---------
  1 | {1,2,7}
(1 row)

postgres=# update t_kenyon set items = items||'{99,66}';
UPDATE 1
postgres=# select * from t_kenyon;
id |      items      
----+------------------
  1 | {1,2,7,55,99,66}
(1 row)

往前插
postgres=# update t_kenyon set items = array_prepend(55,items) ;
UPDATE 1
postgres=# select * from t_kenyon;
id |        items       
----+---------------------
  1 | {55,1,2,7,55,99,66}
(1 row)

d.数据查询

postgres=# insert into t_kenyon(items) values('{3,4,5}');
INSERT 0 1

postgres=# select * from t_kenyon where id = 1;
id |        items       
----+---------------------
  1 | {55,1,2,7,55,99,66}
(1 row)

postgres=# select * from t_kenyon where items[1] = 55;
id |        items       
----+---------------------
  1 | {55,1,2,7,55,99,66}
(1 row)

postgres=# select * from t_kenyon where items[3] = 5;
id |  items 
----+---------
  4 | {3,4,5}
(1 row)

postgres=# select items[1],items[3],items[4] from t_kenyon;
items | items | items
-------+-------+-------
    55 |     2 |     7
     3 |     5 |     
(2 rows)

postgres=# select unnest(items) from t_kenyon where id = 4;
unnest
--------
      3
      4
      5
(3 rows)

e.数组比较

postgres=# select ARRAY[1,2,3] <= ARRAY[1,2,3];
?column?
----------
t
(1 row)

f.数组字段类型转换

postgres=# select array[['11','12'],['23','34']]::int[];
       array      
-------------------
{{11,12},{23,34}}
(1 row)

postgres=# select array[[11,12],[23,34]]::text[];
       array      
-------------------
{{11,12},{23,34}}
(1 row)

3.数组索引

postgres=# create table t_kenyon(id int,items int[]);
CREATE TABLE
postgres=# insert into t_kenyon values(1,'{1,2,3}');
INSERT 0 1
postgres=# insert into t_kenyon values(1,'{2,4}');
INSERT 0 1
postgres=# insert into t_kenyon values(1,'{34,7,8}');
INSERT 0 1
postgres=# insert into t_kenyon values(1,'{99,12}');
INSERT 0 1
postgres=# create index idx_t_kenyon on t_kenyon using gin(items);
CREATE INDEX
postgres=# set enable_seqscan = off;
postgres=# explain select * from t_kenyon where items@>array[2];
                                QUERY PLAN                                 
---------------------------------------------------------------------------
 Bitmap Heap Scan on t_kenyon  (cost=8.00..12.01 rows=1 width=36)
   Recheck Cond: (items @> '{2}'::integer[])
   ->  Bitmap Index Scan on idx_t_kenyon  (cost=0.00..8.00 rows=1 width=0)
         Index Cond: (items @> '{2}'::integer[])
(4 rows)

附数组操作符:
Operator Description Example Result

=	equal	ARRAY[1.1,2.1,3.1]::int[] = ARRAY[1,2,3]	t
<>	not equal	ARRAY[1,2,3] <> ARRAY[1,2,4]	t
<	less than	ARRAY[1,2,3] < ARRAY[1,2,4]	t
>	greater than	ARRAY[1,4,3] > ARRAY[1,2,4]	t
<=	less than or equal	ARRAY[1,2,3] <= ARRAY[1,2,3]	t
>=	greater than or equal	ARRAY[1,4,3] >= ARRAY[1,4,3]	t
@>	contains	ARRAY[1,4,3] @> ARRAY[3,1]	t
<@	is contained by	ARRAY[2,7] <@ ARRAY[1,7,4,2,6]	t
&&	overlap (have elements in common)	ARRAY[1,4,3] && ARRAY[2,1]	t
||	array-to-array concatenation	ARRAY[1,2,3] || ARRAY[4,5,6]	{1,2,3,4,5,6}
||	array-to-array concatenation	ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9]]	{{1,2,3},{4,5,6},{7,8,9}}
||	element-to-array concatenation	3 || ARRAY[4,5,6]	{3,4,5,6}
||	array-to-element concatenation	ARRAY[4,5,6] || 7	{4,5,6,7}

数组函数：
Function Return Type Description Example Result

array_append(anyarray, anyelement)	anyarray	append an element to the end of an array	array_append(ARRAY[1,2], 3)	{1,2,3}
array_cat(anyarray, anyarray)	anyarray	concatenate two arrays	array_cat(ARRAY[1,2,3], ARRAY[4,5])	{1,2,3,4,5}
array_ndims(anyarray)	int	returns the number of dimensions of the array	array_ndims(ARRAY[[1,2,3], [4,5,6]])	2
array_dims(anyarray)	text	returns a text representation of array's dimensions	array_dims(ARRAY[[1,2,3], [4,5,6]])	[1:2][1:3]
array_fill(anyelement, int[], [, int[]])	anyarray	returns an array initialized with supplied value and dimensions, optionally with lower bounds other than 1	array_fill(7, ARRAY[3], ARRAY[2])	[2:4]={7,7,7}
array_length(anyarray, int)	int	returns the length of the requested array dimension	array_length(array[1,2,3], 1)	3
array_lower(anyarray, int)	int	returns lower bound of the requested array dimension	array_lower('[0:2]={1,2,3}'::int[], 1)	0
array_prepend(anyelement, anyarray)	anyarray	append an element to the beginning of an array	array_prepend(1, ARRAY[2,3])	{1,2,3}
array_to_string(anyarray, text [, text])	text	concatenates array elements using supplied delimiter and optional null string	array_to_string(ARRAY[1, 2, 3, NULL, 5], ',', '*')	1,2,3,*,5
array_upper(anyarray, int)	int	returns upper bound of the requested array dimension	array_upper(ARRAY[1,8,3,7], 1)	4
string_to_array(text, text [, text])	text[]	splits string into array elements using supplied delimiter and optional null string	string_to_array('xx~^~yy~^~zz', '~^~', 'yy')	{xx,NULL,zz}
unnest(anyarray)	setof anyelement	expand an array to a set of rows	unnest(ARRAY[1,2])	1 2 (2 rows)

 
参考：http://www.postgresql.org/docs/9.2/static/functions-array.html

原文地址：http://my.oschina.net/Kenyon/blog/133974