ERROR: operator does not exist: jsonb[] -> integer

Question

select id,rules from links where id=2;
 id |                                                                                   rules                                                                                   
----+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  2 | {"{\"id\": \"61979e81-823b-419b-a577-e2acb34a2f40\", \"url\": \"https://www.wikijob.co.uk/about-us\", \"what\": \"country\", \"matches\": \"GB\", \"percentage\": null}"}

我正在尝试使用此处的运算符获取 jsonb 的元素 https://www.postgresql.org/docs/9.6/functions-json.html

无论我使用 'url' 还是下面的整数，我都会得到类似的结果。

select id,rules->1 from links where id=2;
ERROR:  operator does not exist: jsonb[] -> integer
LINE 1: select id,rules->1 from links where id=2;
                       ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.

我做错了什么？

PS Postgres 版本 9.6.12.

Answer 1

该列是一个数组，您可以使用索引访问第一个元素：

select id, rules[1]
from links
where id = 2

一定要检查

在横向连接中使用 jsonb_each() 以在单独的行中查看所有规则：

select id, key, value
from links
cross join jsonb_each(rules[1]) as rule(key, value)
where id = 2

您可以通过这种方式获取单个规则：

select id, value as url
from links
cross join jsonb_each(rules[1]) as rule(key, value)
where id = 2 and key = 'url'

使用unnest()在数组的所有元素中找到一个url，例如：

select id, unnest(rules)->'url' as url
from links
where id = 2;

ERROR: operator does not exist: jsonb[] -> integer

ERROR: operator does not exist: jsonb[] -> integer

arrays

postgresql

json

jsonb