node.js - node中MYSQL的异步问题

问题描述

我在用node查询数据库中使用如下代码：var _password =mysql.query(table,' where name = ' + '’' + name + '’','password');其中mysql.query为query(table,others,column){

var connection = this.connection; var sql; if(column) sql = 'select ' + column + ' from ' + table; else{sql = 'select * from ' + table;} if(others) sql += ' ' + others; console.log(sql); var result; connection.query(sql,function(err,rows,fields){if(err){ throw err;}if(rows.length > 1){ rows.forEach(function(row){console.log(row); });}else if(rows.length == 1){ console.log(rows[0]); rows = rows[0];} else{ console.log('没有数据');}return rows; }); console.log(’result:’); console.log(result); return result;}

最终的结果是：

很显然query之后的语句先执行了，此处无法使用yield，请大神指教

问题解答

rows.forEach(function(row){ console.log(row);});

这里面的循环是异步的，所以出问题了，你要控制住异步。

给你一个例子，我刚学着写，应该写的不咋地，但是可以给你演示如何控制异步。

这里是引用的cc这个model里的，不写全了，大概看一下 getGrades: async () => { return new Promise((resolve, reject) => { db.pool.query(’SELECT * FROM set_grades’, function (err, rows) {if(rows){ resolve(rows);}else{ console.log(err); reject(err);} }); }); }, getTerms: async (grade_id) => { return new Promise((resolve, reject) => { db.pool.query(’SELECT * FROM set_terms WHERE grade_id = ?’, grade_id,function (err, rows) {if(rows){ resolve(rows);}else{ console.log(err); reject(err);} }); }); },// ------------创建合同-------------exports.createContract = async (ctx, next)=> { // 1 获取types let types = new Array(); await cc.getTypes().then(result => { types = result; }); // 2 获取cats let cats = new Array(); await cc.getCats().then(result => { cats = result; }); // 3 获取grades let grades = new Array(); await cc.getGrades().then(result => { grades = result; }); // 4 获取terms // 遍历每一个grades，然后获取下面的terms，合并到grades let forGrades = async function(grades) { for(let grade of grades){ await cc.getTerms(grade.grade_id).then(result => {grade.terms = result; }); } } await forGrades(grades); await ctx.render(’cc/createContract’,{ title: ’Create Contract’, student_id: ctx.params.id, types: types, cats: cats, grades: grades })}