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[英]Isolate an array element inside nested array and use it as the JSON field value with it's sibling array elements as a field value
[英]Query for array elements inside JSON[] field array type
我嘗試使用函數json_array_elements()
JSON 數組,並嘗試使用json_array_length(field_name)
計算數組的元素不成功。 我正在使用 PostgreSQL 9.4.5。
我正在尋找元素"name"
的查詢結果,這是 json 類型數組字段crew
中保存的數據:
[
{
"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
}
]
您的問題源於對 json[] 類型的錯誤使用。 json 數組是單個 json 對象,它的類型是 json,而不是 json[]。 例子:
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
}
]');
函數json_array_elements()
按預期工作:
select id, elem->'name' as name
from test
cross join json_array_elements(crew) elem;
id | name
----+----------
1 | "Ramona"
1 | "Ramon"
(2 rows)
查詢之一(或兩者)應該適用於json[]
:
select id, elem->'name' as name
from test
cross join json_array_elements(crew[1]) elem;
select id, elem->'name' as name
from test
cross join unnest(crew)
cross join json_array_elements(unnest) elem;
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