Postgres jsonb_insert 数组答案

【问题标题】：Postgres jsonb_insert arrayPostgres jsonb_insert 数组
【发布时间】：2021-01-14 13:50:52
【问题描述】：

我正在尝试构建一个查询，该查询返回一组客户购物车及其所有商品，例如

表格：

购物车：id、customer_id

项目：cart_id、price、brand

所需的 JSON 结果示例：

[{
  "id": 1, "customer_id": 1,
  "items": [{
    "price": 14.50, "brand": "Coke"
  }]
}]

失败的 SQL 查询（可在此处测试：http://sqlfiddle.com/#!17/0ef54/1）：

SELECT jsonb_insert(to_jsonb(c.*), 'items', array(
  SELECT to_jsonb(i.*)
  FROM item i
  WHERE i.cart_id = c.id
)
FROM cart c

如何做到这一点？

【问题讨论】：

标签： postgresql postgresql-json

【解决方案1】：

听起来好像您正在寻找聚合：

select jsonb_agg(to_jsonb(c)||jsonb_build_object('items', i.items))
from cart c 
  join (
    select cart_id, jsonb_agg(to_jsonb(i) - 'cart_id') as items
    from item i
    group by cart_id
  ) i on i.cart_id = c.id;

Online example

【讨论】：

试过了，报错：sqlfiddle.com/#!17/0ef54/2
@Werner：抱歉，忘记别名了。查看我的编辑

【解决方案2】：

select jsonb_agg(to_jsonb(c.*) || 
 jsonb_build_object
 (
  'items', 
  (select jsonb_agg(to_jsonb(i.*) - 'cart_id') from item i where c.id = i.cart_id)
 )
) from cart c;

演示

create temporary table item (cart_id integer, price numeric, brand text);
create temporary table cart (id integer, customer_id integer);
insert into item values (1, 10, 'skoda'),(1, 11, 'ford'), (1, 12, 'opel'); 
insert into item values (2, 20, 'skoda'),(2, 21, 'ford'), (2, 22, 'opel'); 
insert into cart values (1, 1), (2, 2);

select jsonb_agg(to_jsonb(c.*) || jsonb_build_object(
 'items', (select jsonb_agg(to_jsonb(i.*) - 'cart_id') from item i where c.id = i.cart_id)
)) from cart c;

结果：

[
  {
    "id": 1,
    "items": [
      {
        "brand": "skoda",
        "price": 10
      },
      {
        "brand": "ford",
        "price": 11
      },
      {
        "brand": "opel",
        "price": 12
      }
    ],
    "customer_id": 1
  },
  {
    "id": 2,
    "items": [
      {
        "brand": "skoda",
        "price": 20
      },
      {
        "brand": "ford",
        "price": 21
      },
      {
        "brand": "opel",
        "price": 22
      }
    ],
    "customer_id": 2
  }
]

【讨论】：