插入数组值 [英] Inserting array values

问题描述

如何编写和执行使用libpqxx插入数组值的查询？

How do I write and execute a query which inserts array values using libpqxx?

INSERT INTO exampleTable(exampleArray[3]) VALUES('{1, 2, 3}');

此示例代码为我提供：

ERROR:  syntax error at or near "'"

什么是错误？在PostgreSQL文档中，我发现：

What is wrong? In PostgreSQL documentation I found that:

CREATE TABLE sal_emp (
name            text,
pay_by_quarter  integer[],
schedule        text[][]
); 

...

INSERT INTO sal_emp
VALUES ('Bill',
'{10000, 10000, 10000, 10000}',
'{{"meeting", "lunch"}, {"training", "presentation"}}');

推荐答案

您应该使用没有索引的列名来插入数组：

You should use a column name without an index to insert an array:

create table example(arr smallint[]);
insert into example(arr) values('{1, 2, 3}');
-- alternative syntax
-- insert into example(arr) values(array[1, 2, 3]);

select * from example;

   arr   
---------
 {1,2,3}
(1 row) 

使用带有索引的列名访问数组的单个元素：

Use the column name with an index to access a single element of the array:

select arr[2] as "arr[2]"
from example;

 arr[2] 
--------
      2
(1 row)

update example set arr[2] = 10;
select * from example;

   arr    
----------
 {1,10,3}
(1 row) 

您可以在 INSERT <中使用 arr [n] / code>，但这有特殊含义。使用这种语法，您可以创建一个数组，其中的一个元素从给定的数字开始索引。

You can use arr[n] in INSERT but this has special meaning. With this syntax you can create an array with one element indexed from the given number:

delete from example;
insert into example(arr[3]) values (1);
select * from example;

    arr    
-----------
 [3:3]={1}
(1 row) 

因此，您有一个下界为3的数组：

As a result you have an array which lower bound is 3:

select arr[3] from example;
 arr 
-----
   1
(1 row)

这篇关于插入数组值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！