Nodejs Mysql query with mysql variables cannot save result

Question

I've been trying to get this query result to save into a variable but no luck. When I run the query from workbench directly I get the result,also if I run it from node, I get the following

set @count=(select column from table where value = 'value');
SET @row_number = 0; 
select column from 
(SELECT 
    (@row_number:=@row_number + 1) AS num, 
   column
FROM
    table where column is null
ORDER BY column)as a
 where num <= @count

this code basically selects X number of rows from tableA according to what ever value is saved to @count

var dnum = []; 
    dbconn.query('SET @row_number = 0;' +
     'set @count=(select column from table where column= "value");' +
     'select column from \n '+ 
     '(SELECT \n' +
     '    (@row_number:=@row_number + 1) AS num, \n' + 
     '   column \n' +
     'FROM \n' +
     '    table where column is null \n' +
     'ORDER BY column )as a \n' +
     'where num <= @count  ;',function(err,rows,result)     {
         console.log(rows)
         dnum = rows or //dnum.push(rows)
     })
     console.log(dnum)

Sample output:

 [
  OkPacket {
    fieldCount: 0,
    affectedRows: 0,
    insertId: 0,
    serverStatus: 10,
    warningCount: 0,
    message: '',
    protocol41: true,
    changedRows: 0
  },
  OkPacket {
    fieldCount: 0,
    affectedRows: 0,
    insertId: 0,
    serverStatus: 10,
    warningCount: 0,
    message: '',
    protocol41: true,
    changedRows: 0
  },
  [
    RowDataPacket { number: '123456789' },
    RowDataPacket { number: '098745612' }
  ]
]

I would like to save the returning RowDataPacket results to a variable to use somewhere else.

Thanks

Answer 1

Should be as easy as:

rows.forEach(row => dnum.push(row.number));

If you're getting multiple results back from multiple queries, you may need to skip to the correct one. This could be done by destructuring the response:

dbconn.query('...', ,function(err,[ _ok1, _ok2, rows ], result) {
  rows.forEach(row => dnum.push(row.number));
}

Where _ok1 and _ok2 are there to just sponge up the "don't care" responses to your SET statements.

Answer 2

Thanks @tadman for all the comments. Apparently my previous query approach did return the expected result, but somehow it was not usable. I was able to achieve this via below code. Not sure how clean or sensible the code is,but it takes care of the job for now.Until I mess up somewhere else:)

function getNumbers(){
    return new Promise(function(resolve, reject) {
    var q = queue ///This part is returned from express frontend
    let sql1 = 'set @count=(select number from table where name= ? )';
    let sql2 = 'SET @row_number = 0';
    let sql3 =  'select number from \n '+ 
    '(SELECT \n' +
    '    (@row_number:=@row_number + 1) AS num, \n' + 
    '   number \n' +
    'FROM \n' +
    '    numbers where isSelected is null \n' +
    'ORDER BY number)as a \n' +
    'where num <= @count  ;'   
 


    dbconn.query(sql1,q, (err, fields) => {
    if (err) {
        return reject(err);
    } 
    
    });
    dbconn.query(sql2, (err,fields) => {
        if (err) {
            return reject(err);
        }
    }) 
        dbconn.query(sql3, (err, rows, fields) => {
            if (err) {
                return reject(err);
            }
            resolve(rows); 
            
        })
    
    })
    }
    //////////////////////////return number//////////////////////////////
    let dnum =[];

    getNumbers().then((rows) => {
    
    for (let i = 0; i < rows.length; i++) 
    
       // console.log(rows[i].number)    
        dnum.push(rows[i].number)
        console.log(dnum)       
    
    })