SQL 右連接到 JSON/數組

Question

我正在嘗試將來自 MySql right join聯接的行數組轉換為 nodeJS 上的array/json格式。 考慮通用的 mysql 表：

emp_id  name
1       john
2       bill
3       anna


fk_emp_id   project
1           p1
1           p2
1           p3
2           p1
2           p4

和他們的正確連接：

id  name fk_emp_id  project
1   john    1       p1
1   john    1       p2
1   john    1       p3
2   bill    2       p1
2   bill    2       p4
3   anna    3       null

這是：

rows = [
    {"id":1, "name":"john", "fk_emp_id" : "1" , "project" : "p1"},
    {"id":1, "name":"john", "fk_emp_id" : "1" , "project" : "p2"},
    {"id":1, "name":"john", "fk_emp_id" : "1" , "project" : "p3"},
    {"id":2, "name":"bill", "fk_emp_id" : "2" , "project" : "p1"},
    {"id":2, "name":"bill", "fk_emp_id" : "2" , "project" : "p4"},
    {"id":3, "name":"anna", "fk_emp_id" : "3" , "project" : null}
]

我如何將它們轉換為這個 JSON：

result = [
    {id: '1',
     name: 'john',
     projects: [p1, p2, p3]
    }
    ,
    {id: '2',
     name: 'bill',
     projects: [p1, p4]
    }
    ,
    {id: '3',
     name: 'anna',
     projects: []
    }
]

Answer 1

如果您只尋找將rows轉換為result數組的版本，那么您可以使用Map作為哈希表來引用給定的id 。

 var rows = [{ id: 1, name: "john", fk_emp_id: "1", project: "p1" }, { id: 1, name: "john", fk_emp_id: "1", project: "p2" }, { id: 1, name: "john", fk_emp_id: "1", project: "p3" }, { id: 2, name: "bill", fk_emp_id: "2", project: "p1" }, { id: 2, name: "bill", fk_emp_id: "2", project: "p4" }, { id: 3, name: "anna", fk_emp_id: "3", project: null }], result = []; rows.forEach(function (a) { var reference = this.get(a.id); if (!reference) { reference = { id: a.id, name: a.name, fk_emp_id: a.fk_emp_id, projects: [] }; this.set(a.id, reference); result.push(reference); } a.project && reference.projects.push(a.project); }, new Map); console.log(result);

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