Question

我正在尝试查询以获取与该报告相关联的report和所有report_items。

reports表结构：id |名称| creation_date

report_items表结构：id | report_id |地方制片人|序列号

我尝试过：

SELECT "reports".*,
          to_json("report_items".*) as "items"
          FROM "reports" INNER JOIN "report_items" USING ("id")
          WHERE "reports".id = ${req.params.id}

但只有第一个report_item返回（而不是report_items列表）：

{"id":1,"type":"fd","name":"dsfdsfds","client_name":"fdsfds","website":"dsffds","creation_time":"2019-03-12T22:00:00.000Z","items":{"id":1,"report_id":1,"place":"saddsa","type":"sdadsa","producer":"sdadsa","serial_number":"adsdsa","next_check_date":"2019-03-19","test_result":"saddsa","comments":"saddsa"}}

预期结果：

{"id":1,"type":"fd","name":"dsfdsfds","client_name":"fdsfds","website":"dsffds","creation_time":"2019-03-12T22:00:00.000Z","items": [{"id":1,"report_id":1,"place":"saddsa","type":"sdadsa","producer":"sdadsa","serial_number":"adsdsa","next_check_date":"2019-03-19","test_result":"saddsa","comments":"saddsa"}, {"id":1,"report_id":1,"place":"saddsa","type":"sdadsa","producer":"sdadsa","serial_number":"adsdsa","next_check_date":"2019-03-19","test_result":"saddsa","comments":"saddsa"}]}

知道我缺少什么吗？

我可以做的一个很长的解决方案（肯定不是很理想。）：

SELECT * FROM reports
        WHERE id = ${req.params.id}

SELECT * FROM report_items
      WHERE report_id = ${req.params.id}

并通过编程将它们组合在一起。

Answer 1

如果我对问题的理解正确，那么期望的结果是将报告数据包含一行作为JSON数组的所有内容。

在此假设下，以下查询应起作用：

WITH data (id, items) AS (
    SELECT report_id, array_to_json(array_agg(to_json(*)))
    FROM report_items WHERE report_id = ${req.params.id}
    GROUP BY report_id
)
SELECT reports.*, data.items
FROM reports
INNER JOIN data ON (reports.id = data.report_id)
WHERE reports.id = ${req.params.id}

...或作为子选择（因为PostgreSQL不够聪明，无法将过滤器推入CTE：

SELECT reports.*, data.items
FROM reports
INNER JOIN (SELECT report_id, array_to_json(array_agg(to_json(report_items.*)))
    FROM report_items
    GROUP BY report_id) AS data (id, items) ON (reports.id = data.id)
WHERE reports.id = ${req.params.id}

在两种情况下，输出列items将包含所有相关项目的JSON数组。

如果您希望将完整的报告条目作为JSON，请尝试以下操作（请注意，此操作仅适用于jsonb，不适用于json）：

SELECT jsonb_set(to_jsonb(reports.*), '{items}', data.items, true) AS report_data
FROM reports
INNER JOIN (SELECT report_id, array_to_json(array_agg(to_json(report_items.*)))::jsonb
    FROM report_items
    GROUP BY report_id) AS data (id, items) ON (reports.id = data.id)
WHERE reports.id = ${req.params.id}

Postgres-查询一对多关系

1 个答案: