Question

我有一个表格形式的数据库表

CREATE TABLE products(
 id SERIAL PRIMARY KEY,
 category TEXT,
 name TEXT,
 price REAL,
 weight REAL);

，我想以

格式为我的API输出JSON。

[{"category":"category name", 
"products":[{"name":"product name one","price":4.44,"weight":0.5}, 
{"name":"product name two","price":6.45,"weight":1.0}]}]

因此，如果我的表中包含以下条目：

INSERT INTO products (category, name, price, weight) 
VALUES ("toothpaste","Chrest Pro-White",4.99,6.4),
("toothpaste","Colgate Cavity Prevention",3.99,6.4), 
("body wash","Old Spice Hydro",5.99,16.0), 
("body wash","Axe Apollo",8.99,22.0);

API应该返回

[{"category":"toothpaste", 
"products":[{"name":"Chrest Pro-White","price":4.99,"weight":6.4}, 
{"name":"Colgate Cavity Prevention","price":3.99,"weight":6.4}]},
{"category":"body wash", 
"products":[{"name":"Old Spice Hydro","price":5.99,"weight":16.0}, 
{"name":"Axe Apollo","price":8.99,"weight":22.0}]}]

我可以遍历表中的所有行，并为每个唯一的类别名称手动创建json对象，但是我希望有一种更好的方法。

Answer 1

有很多方法可以通过使用ORM并从API服务器创建json来实现，但是您也可以直接在postgres中实现：

select json_agg(categories) 
FROM (
  SELECT json_build_object(
         'category', category,
         'products', json_agg(
                        json_build_object(
                           'name', name, 
                           'price', price, 
                           'weight', weight)
                        )
       ) as categories
FROM products
GROUP BY category) sub;
[{"category" : "toothpaste", "products" : [{"name" : "Chrest Pro-White", "price" : 4.99, "weight" : 6.4}, {"name" : "Colgate Cavity Prevention", "price" : 3.99, "weight" : 6.4}]}, {"category" : "body wash", "products" : [{"name" : "Old Spi
ce Hydro", "price" : 5.99, "weight" : 16}, {"name" : "Axe Apollo", "price" : 8.99, "weight" : 22}]}]

Answer 2

您可以使用此 console.log（JSON.stringify（data））;

将来自SQL查询的数据格式化为JSON

2 个答案: