sql - 向 Json 数组添加新元素

Question

我想在 json 下面的 a3 中添加一个新的数组元素:

{
    "a1": "e1",
    "a2": {
        "b1": "y1",
        "b2": "y2"
    },
    "a3": [{
            "arr1": "1"
        },
        {
            "arr2": "2"
        }
    ]
}

所以我希望上面的 json 是这样的:

{
    "a1": "e1",
    "a2": {
        "b1": "y1",
        "b2": "y2"
    },
    "a3": [{
            "arr1": "1"
        },
        {
            "arr2": "2"
        },
        {
            "arr3": "3"
        }
    ]
}

我可以使用以下命令添加新元素。但是当涉及到数组时，我找不到添加新元素的方法。

SELECT jsonb_set('{ "a1": "e1", "a2": { "b1": "y1", "b2": "y2" }, "a3": [{ "arr1": "1" }, { "arr2": "2" }] }'::jsonb,
'{a2,b3}', 
'"4"');

我应该使用什么命令将 { "arr3": "3"} 添加到 a3？

编辑:如果 arr3 已经存在，命令应该改变它的值。不应添加重复的 {"arr3":"3"}。

Answer 1

对数组使用连接运算符||:

with my_data(json_data) as (
values
    ('{ "a1": "e1", "a2": { "b1": "y1", "b2": "y2" }, "a3": [{ "arr1": "1" }, { "arr2": "2" }] }'::jsonb)
)

select jsonb_set(json_data, '{a3}', json_data->'a3' || '{"arr3": "3"}')
from my_data;

                                             jsonb_set                                             
---------------------------------------------------------------------------------------------------
 {"a1": "e1", "a2": {"b1": "y1", "b2": "y2"}, "a3": [{"arr1": "1"}, {"arr2": "2"}, {"arr3": "3"}]}
(1 row)

检查键是否存在于嵌套数组中有点复杂。您应该使用 jsonb_array_elements() 取消嵌套数组来执行此操作:

with my_data(json_data) as (
values
    ('{ "a1": "e1", "a2": { "b1": "y1", "b2": "y2" }, "a3": [{ "arr1": "1" }, { "arr2": "2" }] }'::jsonb)
)

select 
    case when already_exists then json_data
    else jsonb_set(json_data, '{a3}', json_data->'a3' || '{"arr3": "3"}')
    end as json_data
from (
    select json_data, bool_or(value ? 'arr3') as already_exists
    from my_data
    cross join jsonb_array_elements(json_data->'a3')
    group by 1
    ) s