javascript - Node MySql Callback for Multiple Queries -

i ran issue whilst attempting create logic add rows new table made on mysql database. when adding row need query database 4 times check other rows , add correct value new row. using node.js , mysql module accomplish this. while coding ran snag, code not wait 4 queries finish before inserting new row, gives values being found value of 0 every time. after research realize callback function in order, looking this:

var n = 0; connection.query("select...", function(err, rows){     if(err) throw err;     else{         if(rows.length === 1) ++n;     }     callback(); });  function callback(){     connection.query("insert...", function(err){          if(err) throw err;     }); } 

note: select queries can return 1 item if condition should not effect issue.

a callback function 1 query wait on clear me, become bit lost multiple queries wait on. idea had create variable increments before callback called, , passed in callback function's arguments. inside callback query encapsulated if statement condition of being variable equaling number of queries need called, 4 purposes here. see working wasn't sure if sort of situation has built in solution or if there other, better, solutions developed.

you need async (https://github.com/caolan/async). can complex logic module.

var data = {} //you can in many ways 1 way defining global object can add things object , every function can see  firstqueryfunction(callback){     //do stuff mysql     data.stuff = rows[0].stuff; //you can store stuff inside data object     callback(null);  }  secondqueryfunction(callback){     //do stuff mysql     callback(null); }  thirdqueryfunction(callback){     //do stuff mysql     callback(null); }  fourthqueryfunction(callback){     //do stuff mysql     callback(null); }  //this functions executed @ same time async.parallel([     firstqueryfunction,     secondqueryfunction,     thirdqueryfunction,     fourthqueryfunction ], function (err, result) {      //this code executed after previous queries done (the order doesn't matter).      //for example can query depends of result of previous queries. });