Postgres数组使用-MySQL-Tutorial-php.cn

Postgres数组使用环境： 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]] --

Postgres数组使用

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"

--------+-----------+-------------------------------------------------------+----------+--------------+-------------

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"

--------+-----------+----------------------------------------------------+----------+--------------+-------------

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 rows)

e.数组比较

postgres=# select ARRAY[1,2,3]

?column?

----------

(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] t

> greater than ARRAY[1,4,3] > ARRAY[1,2,4] t

less than or equal 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] 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])

(2 rows)