PostgreSQL数组使用

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 ~]$ psqlpsql (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 TABLEpostgres=# \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: nopostgres=# 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 TABLEpostgres=# \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 1postgres=# insert into t_kenyon(items) values('{3,4,5}');INSERT 0 1postgres=# insert into t_kenyon(items) values(array[6,7,8,9]);INSERT 0 1postgres=# 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 1postgres=# delete from t_kenyon where items[1] = 4;DELETE 0postgres=# 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 1postgres=# select * from t_kenyon;id |  items ----+---------  1 | {1,2,7}(1 row)postgres=# update t_kenyon set items = items||'{99,66}';UPDATE 1postgres=# 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 1postgres=# 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 1postgres=# 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 TABLEpostgres=# insert into t_kenyon values(1,'{1,2,3}');INSERT 0 1postgres=# insert into t_kenyon values(1,'{2,4}');INSERT 0 1postgres=# insert into t_kenyon values(1,'{34,7,8}');INSERT 0 1postgres=# insert into t_kenyon values(1,'{99,12}');INSERT 0 1postgres=# create index idx_t_kenyon on t_kenyon using gin(items);CREATE INDEXpostgres=# 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: 
OperatorDescriptionExampleResult=equalARRAY[1.1,2.1,3.1]::int[] = ARRAY[1,2,3]t<>not equalARRAY[1,2,3] <> ARRAY[1,2,4]t<less thanARRAY[1,2,3] < ARRAY[1,2,4]t>greater thanARRAY[1,4,3] > ARRAY[1,2,4]t<=less than or equalARRAY[1,2,3] <= ARRAY[1,2,3]t>=greater than or equalARRAY[1,4,3] >= ARRAY[1,4,3]t@>containsARRAY[1,4,3] @> ARRAY[3,1]t<@is contained byARRAY[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 concatenationARRAY[1,2,3] || ARRAY[4,5,6]{1,2,3,4,5,6}||array-to-array concatenationARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9]]{{1,2,3},{4,5,6},{7,8,9}}||element-to-array concatenation3 || ARRAY[4,5,6]{3,4,5,6}||array-to-element concatenationARRAY[4,5,6] || 7{4,5,6,7}

数组函数： 
FunctionReturn TypeDescriptionExampleResultarray_append(anyarray, anyelement)anyarrayappend an element to the end of an arrayarray_append(ARRAY[1,2], 3){1,2,3}array_cat(anyarray, anyarray)anyarrayconcatenate two arraysarray_cat(ARRAY[1,2,3], ARRAY[4,5]){1,2,3,4,5}array_ndims(anyarray)intreturns the number of dimensions of the arrayarray_ndims(ARRAY[[1,2,3], [4,5,6]])2array_dims(anyarray)textreturns a text representation of array's dimensionsarray_dims(ARRAY[[1,2,3], [4,5,6]])[1:2][1:3]array_fill(anyelement, int[], [, int[]])anyarrayreturns an array initialized with supplied value and dimensions, optionally with lower bounds other than 1array_fill(7, ARRAY[3], ARRAY[2])[2:4]={7,7,7}array_length(anyarray, int)intreturns the length of the requested array dimensionarray_length(array[1,2,3], 1)3array_lower(anyarray, int)intreturns lower bound of the requested array dimensionarray_lower('[0:2]={1,2,3}'::int[], 1)0array_prepend(anyelement, anyarray)anyarrayappend an element to the beginning of an arrayarray_prepend(1, ARRAY[2,3]){1,2,3}array_to_string(anyarray, text [, text])textconcatenates array elements using supplied delimiter and optional null stringarray_to_string(ARRAY[1, 2, 3, NULL, 5], ',', '*')1,2,3,*,5array_upper(anyarray, int)intreturns upper bound of the requested array dimensionarray_upper(ARRAY[1,8,3,7], 1)4string_to_array(text, text [, text])text[]splits string into array elements using supplied delimiter and optional null stringstring_to_array('xx~^~yy~^~zz', '~^~', 'yy'){xx,NULL,zz}unnest(anyarray)setof anyelementexpand an array to a set of rowsunnest(ARRAY[1,2])

12

(2 rows)
  
参考：http://www.postgresql.org/docs/9.2/static/functions-array.html