Addition, deletion, modification, and query of PostgreSQL array types

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foreword

PostgreSQL supports fixed-length or variable-length one-dimensional or multi-dimensional arrays for table fields, and the type of the array can be any database built-in type, user-defined type, enumeration type, and composite type.
The definition of the array type is realized by adding square brackets [] behind its basic type, and a length number can be given or not in the square brackets.

1. Define the array type

First of all, we first created the t_test table, which contains the array field name of type int and the array field address of type text, as shown in the following code snippet.

create table t_test (
	id bigint,
	name integer[],
	address text[]
);

2. Array type insert data

Method 1: Use {} to convert data into an array

insert into t_test(id,name,address) values(1,'{1,2}','{"beijing","shanghai"}');

Method 2: Use array to convert data into an array

insert into t_test(id,name,address) values(2,array[1,2],array['beijing','shanghai']);

The result after insertion is shown in the figure below.

3. Array type modify data

Append array elements at the end: You can use the array_append function or use ||.

--使用||修改
update t_test set name = name||'{3}' , address = address||'{"shenzhen"}' where id=1;
--使用array_append函数修改
update t_test set name = array_append(name,3) , address = array_append(address,'shenzhen') where id=1;

Append array elements to the head: use the array_prepend function

update t_test set name = array_prepend(3,name) , address = array_prepend('shenzhen',address) where id=2;

4. Array type delete data

Delete the entire row of data by array type.

--如果name数组的第二个元素为1，则删除整行数据
delete from t_test where name[2] = 1;

If you want to delete an element in the array, you need to use the array_remove function with the update statement to achieve, the code is as follows.

update t_test set name= array_remove(name,3) where id=2;

5. Array type query data

Query an element in the array, such as querying the address array and the second element of the address array

select address,address[2] from t_test;

Query the data row containing 3 elements in the name array

select * from t_test where array_position(name,3)>0;

6. Array type operators

The following operators are used for processing or judging between arrays.

operator	describe	example	result
=	equal	ARRAY[1,2,3] = ARRAY[1,2,3]	true
<>	not equal to	ARRAY[1,2,3] <> ARRAY[1,2,4]	true
<	less than	ARRAY[1,2,3] < ARRAY[1,2,4]	true
>	more than the	ARRAY[1,4,3] > ARRAY[1,2,4]	true
<=	less than or equal to	ARRAY[1,2,3] <= ARRAY[1,2,3]	true
>=	greater than or equal to	ARRAY[1,4,3] >= ARRAY[1,4,3]	true
@>	Include	ARRAY[1,4,3] @> ARRAY[3,1]	true
<@	contained in	ARRAY[2,7] <@ ARRAY[1,7,4,2,6]	true
&&	overlap (have common elements)	ARRAY[1,4,3] && ARRAY[2,1]	true
||	Array to Array Concatenation	ARRAY[1,2,3] || ARRAY[4,5,6]	{1,2,3,4,5,6}

7. Commonly used functions of array type

function	illustrate	sentence	result
array_append	Add an element to the end of the array	array_append(ARRAY[1,2], 3)	{1,2,3}
array_prepend	Add a function to the beginning of an array	array_prepend(1, ARRAY[2,3])	{1,2,3}
array_cat	concatenates two arrays	array_cat(ARRAY[1,2,3], ARRAY[4,5])	{1,2,3,4,5}
array_replace	Replaces each array element equal to a given value with a new value	array_replace(ARRAY[1,2,5,4], 5, 3)	{1,2,3,4}
array_remove	Deletes an array element with a given value	array_remove(ARRAY[1,2,3,4],4)	{1,2,3}
[start:end]	Range array elements by subscript	select (ARRAY[‘a’,‘b’,‘c’,‘d’])[1:2]	{a,b}
array_position	The position at which the specified element occurs in the array	array_position(ARRAY[1,8,3,7], 8)	2
array_dims	Returns a textual representation of the array's dimensions	array_dims(ARRAY[[1,2,3], [4,5,6]])	[1:2][1:3]
array_lower	Returns the lower bound of the array dimension	array_lower(ARRAY[1,2,3,4], 1)	1
array_upper	Returns the upper bound of the array dimension	array_upper(ARRAY[1,2,3,4], 1)	4
array_ndims	Returns the dimension of the array	array_ndims(ARRAY[[1,2,3], [4,5,6]])	2
array_length	Returns the length of an array dimension	array_length(array[1,2,3], 1)	3
cardinality	Returns the total number of elements in the array, or 0 if the array is empty	cardinality(ARRAY[1,2,3,5])	4
array_to_string	Convert array to string, concatenate array elements with delimiter	select array_to_string(ARRAY[1, 2, 3], ‘,’)	1,2,3
string_to_array	Splits a string into array elements using the specified delimiter	select string_to_array(‘a,b,c’,‘,’)	{a,b,c}
array_agg	Combine multiple values ​​into an array	SELECT id, array_agg(label) FROM t_label group by id	{label1,label2}
please	decompose an array into a set of rows	select unnest(ARRAY[1,2,3])	1 2 3