Updating multiple rows with node-mysql, NodeJS and Q

Question

I am using node-mysql, node-js, and Q promises.

I have successfully updated, deleted, and inserted single rows using the above. As well as inserted multiple rows in a single statement in my test case scenario.

However, I need to update multiple rows with different values (batch mode) either in a single query or in a for loop.

The information on how to use prepared statements in mysql2 (supposed to improve on node-mysql) is very sparse and there are no examples, although that should be the natural choice, together with promises to compensate for node-js asynchronous nature.

In addition, I have successfully used defered.makeNodeResolver() in various test scenarios.

I am trying to update multiple rows in a single query with a where clause and changing conditions.

It is working when I update a single row. However, when I try to update multiple rows with a single query, the records aren't updated.

I am ready to switch to using a for loop to perform multiple updates and then aggregate the result and send it back from the server to the client, which would have been my second preferred choice. And I don't see why it shouldn't be done that way if there isn't too much of a performance hit. But I haven't found any examples for doing it that way.

var values = [
    { users: "tom", id: 101 },
    { users: "george", id: 102 }
    ];

    // var params = [values.users, values.id ];

    var sql = 'UPDATE tabletest SET users = ? WHERE id = ?;';


    connection.query(sql, [{users: values[0].users}, {id: values[0].id }], defered.makeNodeResolver());

The code shown above isn't actually updating multiple rows. I imagine there's an error in my syntax.

But anyway, what is the best approach to go about this in this particular scenario? Prepared statements, repeated queries in a for loop, or stored procedures?

Answer 1

You can do it this way:

var values = [
  { users: "tom", id: 101 },
  { users: "george", id: 102 }
];
var queries = '';

values.forEach(function (item) {
  queries += mysql.format("UPDATE tabletest SET users = ? WHERE id = ?; ", item);
});

connection.query(queries, defered.makeNodeResolver());

To use multiple statements feature you have to enable it for your connection:

var connection = mysql.createConnection({
  ...
  multipleStatements: true,
});

Answer 2

I don't think you can (at least easily/efficiently) update multiple rows in the way you are trying. You would basically have to loop over your values and execute an UPDATE for each object.

Answer 3

this piece of code was taken from vcl.js for node.js, it is written in typescript and provides a multiple update,delete,inseer statment's in a single transaction.

export class SQLStatment {
    sql: string;
    params: Object
}

var dbError: string;
var execCount: number = 0;
function DBexecuteBatchMYSQLSingle(connection: any, SQLStatmentArray: Array<SQLStatment>, index: number, callback: () => void) {
    execCount++;
    connection.query(SQLStatmentArray[index].sql, SQLStatmentArray[index].params, function (err, rows, fields) {
        if (err) dbError = err;
        if (index + 1 == SQLStatmentArray.length) callback();
        else {
            if (!dbError) {
                DBexecuteBatchMYSQLSingle(connection, SQLStatmentArray, index + 1, function () {
                    if (index == 0) callback();
                });
            }
        }
    });
}

function DBBatchUpdateMYSQL(SQLStatmentArray: Array<SQLStatment>, callback?: (err) => void) {
    var mysql = require('mysql');
    var connection = mysql.createConnection({
        host: "host",user: "user",database: "db",
        port: 1022, password: "pass"});
    dbError = null;
    execCount = 0;
    connection.beginTransaction(function (err) {
        if (err && callback) callback("Database error:" + err);
        else {
            DBexecuteBatchMYSQLSingle(connection, SQLStatmentArray, 0, () => {
                if (dbError) {
                    connection.rollback(function () {
                        if (callback) callback("Database error:" + dbError);
                    });
                } else {
                    connection.commit(function (err) {
                        if (callback) callback(null);
                    })
                }
            });
        }
    });
}

Answer 4

You should probably do following way

UPDATE DB.table
SET table.row = newValue WHERE table.someColumn in ('columnVal1', 'columnVal2');

ex.

UPDATE DB.Students
SET result = "pass" WHERE rollNo in (21, 34, 50);

Answer 5

Don't know if this problem it's still relevant but I will give my 2 cents:

The solution that I found is to use Promise.all

Basically you need to build an array of promises, where every promise is an update statement:

const getUpdatePromise = (row) => {
  return new Promise( (resolve, reject) => {
    mysqlConnection.query('UPDATE tableName SET foo = ? WHERE bar = ?', [row[0], row[1], (error, results, fields) => {
      if (error) reject(error)
      resolve(results)
    });
  })
}

You add this new Promise into an array and pass the final array with all the update statements to the Promise.all function.

It worked for me. Hope it works for someone else.