PostgreSQL - join语句重复行数据组合成单行

Question

我正在加入3个表并获取某些列的重复数据。我想将数据合并到一行。

以下是数据库结构和数据。

CREATE TABLE customers (
    id integer NOT NULL,
    fname character varying(50),
    lname character varying(50)
);

COPY customers (id, fname, lname) FROM stdin;
1   Thomas  Jefferson
2   Benjamin    Franklin
\.

CREATE TABLE customers_products (
    id integer NOT NULL,
    customers_id integer,
    products_id integer,
    account_info json
);

COPY customers_products (id, customers_id, products_id, account_info) FROM stdin;
1   1   1   {"account_number":"000001", "date":"05/28/15"}
2   1   2   {"account_number":"000002", "date":"05/28/15"}
3   2   1   {"account_number":"000003", "date":"05/28/15"}
4   2   3   {"account_number":"000004", "date":"05/28/15"}
\.

CREATE TABLE products (
    id integer NOT NULL,
    name character varying(128)
);

COPY products (id, name) FROM stdin;
1   checking
2   savings
3   credit card
\.

这是我正在使用的查询。

SELECT
    c.id,
    c.fname,
    c.lname,
    p.name,
    cp.account_info
FROM
    customers c
INNER JOIN
    customers_products cp
ON
    c.id = cp.customers_id
INNER JOIN
    products p
ON
    p.id = cp.products_id

这是结果数据集。

如何将数据集重新分成两行，并将帐户信息合并为一行？这是我想要最终得到的数据结构。

[
    {
        "id": 1,
        "fname": "Thomas",
        "lname": "Jefferson",
        "account_info": [
            {
                "name": "checking",
                "account_number":"000001",
                "date":"05/28/15"
            },
            {
                "name": "savings",
                "account_number":"000002",
                "date":"05/28/15"
            }
        ]
    },
    {
        "id": 2,
        "fname": "Benjamin",
        "lname": "Franklin",
        "account_info": [
            {
                "name": "checking",
                "account_number":"000003",
                "date":"05/28/15"
            },
            {
                "name": "credit card",
                "account_number":"000004",
                "date":"05/28/15"
            }
        ]
    }
]

  

解决方案是：

SELECT
    c.id,
    c.fname,
    c.lname,
    string_agg(p.name, ', '),
    json_agg(cp.account_info)
FROM
    customers c
INNER JOIN
    customers_products cp
ON
    c.id = cp.customers_id
INNER JOIN
    products p
ON
    p.id = cp.products_id
GROUP BY
    c.id, c.fname, c.lname
ORDER BY
    c.id;