查询JSON[]字段数组类型中的数组元素

Question

我尝试使用函数JSON\u array\u elements（）卸载JSON数组，并尝试使用JSON\u array\u length（field\u name）计算数组的元素，但没有成功。我使用的是PostgreSQL 9.4.5。

我想查询元素“name”的结果，这是json类型数组field crew | json[]上保存的数据。

crew": [
        {
            "workHours": "9",
            "workers": "50",
            "checker_rate": 100,
            "rate": 150,
            "name": "Ramona",
            "last": null,
            "boxRate": 2,
            "checkTraining": false,
            "editing": true,
            "ix": 0,
            "breakPay": 3.0833333333333335,
            "trainingPay": 0
        },
        {
            "workHours": "4",
            "workers": "50",
            "checker_rate": 120,
            "rate": 160,
            "name": "Ramon",
            "last": "Rosas",
            "boxRate": 2,
            "checkTraining": false,
            "editing": false,
            "id": 1,
            "breakPay": 1.5416666666666667,
            "trainingPay": 0
        }
    ]

Answer 1

您的问题源于对json[]类型的错误使用。json数组是单个json对象，其类型是json，而不是json[]。示例：

create table test (id int, crew json);
insert into test values
(1, '
[
    {
        "workHours": "9",
        "workers": "50",
        "checker_rate": 100,
        "rate": 150,
        "name": "Ramona",
        "last": null,
        "boxRate": 2,
        "checkTraining": false,
        "editing": true,
        "ix": 0,
        "breakPay": 3.0833333333333335,
        "trainingPay": 0
    },
    {
        "workHours": "4",
        "workers": "50",
        "checker_rate": 120,
        "rate": 160,
        "name": "Ramon",
        "last": "Rosas",
        "boxRate": 2,
        "checkTraining": false,
        "editing": false,
        "id": 1,
        "breakPay": 1.5416666666666667,
        "trainingPay": 0
    }
]');

函数json\u array\u elements（）按预期工作：

select id, elem->'name' as name
from test, json_array_elements(crew) elem;

 id |   name   
----+----------
  1 | "Ramona"
  1 | "Ramon"
(2 rows)

其中一个查询（或两者）应能很好地与json[]配合使用：

select id, elem->'name' as name
from test, json_array_elements(crew[1]) elem;

select id, elem->'name' as name
from test, unnest(crew), json_array_elements(unnest) elem;