Nodejs loop through mysql Query give result = undefined

Question

i have a Json Object and want to loop thorugh it. In my loop I want to execute a select query and save it result to another json Array.

So I start with a loop, performe a mysql query and want just log the results:

for (var x = 0; x < obj.length; x++) {
     var query = connection.query('SELECT Id, date FROM tbl1 WHERE Id LIKE '+ mysql.escape(obj[x].ident) +'; SELECT Id, date FROM tbl WHERE Id LIKE '+ mysql.escape(obj[x].ident) +' ORDER BY date DESC Limit 1 offset 1', function (error, results, fields) {
            if (error) {throw error;}
            if (!error) {
                console.log("resultset"+results); //<- Here I get the right result
                console.log("ID: "+results[0].Id); //<- UNDEFINED
                console.log("ID-LAST-entry: "+ results[1].Id); //<- UNDEFINED
                          } });

The Problem is that for booth results (0 and 1) i get = UNDEFINED.

Where is my mistake?

Do you have an Id field within each result object in results? — Master Po
– Master Po, Commented May 27, 2017 at 15:27
Can you share the result of console.log("resultset"+results);? — Master Po
– Master Po, Commented May 27, 2017 at 15:31
ok there we go. My resultset log = resultset:[object Object],[object Object]! — Ckappo
– Ckappo, Commented May 28, 2017 at 8:59

Master Po · Accepted Answer · 2017-06-02 19:46:19Z

1

From the value of results, You can see that it is NOT an array of objects instead it is an array of arrays where each item is an object. You need to iterate inner array to get the Id. See the snippet below. Parsing the result into JSON and then reads the required data.

if (!error) {

    var parsedResults = JSON.parse(JSON.stringify(results));
    var outerArraySize = parsedResults.length;

    for (var outerIndex = 0; outerIndex < outerArraySize; ++outerIndex) {
        var innerArraySize = parsedResults[outerIndex].length;
        for (var innerIndex = 0; innerIndex < innerArraySize; ++innerIndex)
            console.log("ID: " + parsedResults[outerIndex][innerIndex].Id);
    }
}

edited Jun 2, 2017 at 19:46

answered Jun 2, 2017 at 15:53

Master Po

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7 Comments

Ckappo Over a year ago

I still get -> ID: undefined

Master Po Over a year ago

Isn't the results is of the form [[{"Id":"xx123","date":2017-05-24 19:59:21 }],[{"Id":"xx456","date":2017-05-24 19:59:21 }]] ?

Ckappo Over a year ago

the (stringify) result is : [{"Id":"xxx123","date":2017-05-24 19:59:21}] [{"Id":"xxx124","date":2017-05-24 20:00:01}] [{"Id":"xxx125","date":2017-05-24 20:00:03}]

Master Po Over a year ago

Okay! That's different from one provided earlier. We don't have an outer [] there. right?

Master Po Over a year ago

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