將SQL右對齊連接到JSON/array

Question

我試圖將來自MySql right join的行數組轉換爲nodeJS上的array/json格式。考慮到一般的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 

和右加入他們的：

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 

那就是：

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} 
] 

如何將它們轉換爲這個JSON：

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

Answer 1

如果你只看一個版本t o將rows轉換爲result數組，然後您可以使用Map作爲給定id的引用的哈希表。

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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