Question

我试图找出我的数据库表中是否存在记录。如果那里不存在，那么我想将它添加到我的数据库中。我使用节点并使用async.waterfall。但是我的代码出了问题，我找不到什么。它不会将记录添加到我的数据库中。有什么建议吗？

var mysql       = require('mysql');
var connection  = mysql.createConnection({
  host     : 'localhost',
  user     : 'user',
  password : 'password',
  database : 'database'
});


for (var m = 0; m <= (urls.length-1); m++) {
     var Myurl = urls[m];
     var ThisName= TheNames[m];

     //IIFE function. I omitted the error handling for clarity.

     (function(Myurl,ThisName){

        async.waterfall([

          //First find out if the record exists in mydata
          function(next){
          connection.query('SELECT * FROM mydata WHERE UrlLink=?   
                            LIMIT 1',[Myurl],next)
                        },

          //If the record does not exist, put it in mydata
          function(results,next){
          if (results.length==false){
              console.log("New Thing!");
              //Do some stuff here, request(Myurl...) to find TableName.
              var post  = {UniqueUrl:Myurl,ThingName:ThisName,TheName:TableName};
              connection.query('Insert INTO mydata Set ?', post,next);
                                    };
                                };
                         ],

          //Final callback
          function(err, results) {
          connection.end();
                                 };
                       );
     })(Myurl,ThisName);
   };

EDIT：

我在TypeError: object is not a function的{{1}}行找到了回答return next()的错误。在我的真实代码中，我实际上做了类似的事情（当我使用建议的答案时）：

if statement

我真的陷入async.series([ //First function function(callback){ //Some calculations... callback(); }, //Next function function(callback){ var i = 0; //Loop async.whilst( function() { return i <= thefooz.length-1; }, //The innerCallback: function(innerCallback){ //Some calculations where i get urls and TheNames. async.forEachOf(urls, function(Myurl, m, eachDone) { var ThisName = TheNames[m]; async.waterfall([ function(next) { connection.query( 'SELECT * FROM mydata WHERE UrlLink=? LIMIT 1', [ Myurl ], next ); }, function(results, next) { if (results.length !== 0) { return next(); } console.log("New Thing!"); //Do some stuff here, request(Myurl...) to find TableName. var post = { UniqueUrl : Myurl, ThingName : ThisName, TheName : TableName }; connection.query('Insert INTO mydata Set ?', post, next); } ], eachDone); }, function(err) { if (err) throw err; // or however you like to handle errors connection.end(); }); setTimeout(function() { i++; innerCallback(); }, 10000); }); //close my calculations in innerCallback. }, //close innerCallback. ); //close asyns.whilst callback; } //close function(callback) ], function(error){ if (error) return next(error); }); ......

Answer 1

一个（未经测试的）版本应该做同样的事情，但在利用async的更多优点方面有一些错误修正和增强功能：

var mysql      = require('mysql');
var connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'user',
  password : 'password',
  database : 'database'
});

// Process all url's in parallel (at the same time). If you to process them
// sequentially (one after another), you can use `async.forEachOfSeries()`
// instead. Or, if you want to limit the number of parallel requests, use
// `async.forEachOfLimit()`.

async.forEachOf(urls, function(Myurl, m, eachDone) {
  var ThisName = TheNames[m];

  async.waterfall([
    function(next) {
      connection.query(
        'SELECT * FROM mydata WHERE UrlLink=? LIMIT 1',
        [ Myurl ],
        next
      );
    },
    function(results, fields, next) {
      if (results.length !== 0) {
        return next();
      }
      console.log("New Thing!");
      //Do some stuff here, request(Myurl...) to find TableName.
      var post = {
        UniqueUrl : Myurl,
        ThingName : ThisName,
        TheName   : TableName
      };
      connection.query('Insert INTO mydata Set ?', post, next);
    }
  ], eachDone);

}, function(err) {
  if (err) throw err; // or however you like to handle errors
  connection.end();
});

您也可以使用forEach*，而不是使用each*，但由于您需要数组索引forEach*更方便。

Mysql和节点async.waterfall

1 个答案: