SQL right join to JSON/array

Question

I'm trying to convert an array of rows coming from a MySql right join into an array/json format on nodeJS. Considering the generic mysql tables:

emp_id  name
1       john
2       bill
3       anna


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

And a right join of them:

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

Which is:

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}
]

How do I convert them to this JSON:

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

You can use Json-lib from below url to convert it to formatted the JSON. json-lib.sourceforge.net — Karpak
– Karpak, Commented Sep 19, 2016 at 16:20

Nina Scholz · Accepted Answer · 2016-09-19 17:21:46Z

1

If you look only for a version to convert your rows to result array, then you could use a Map as hash table for the reference of the given 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);

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Sep 19, 2016 at 17:21

answered Sep 19, 2016 at 16:55

Nina Scholz

388k26 gold badges367 silver badges417 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

SQL right join to JSON/array

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related