节点。js + MySQL不会得到结果或响应Console.log

I am new to Node.js. I wrote this code:

我是新手。我写的这段代码:

db.query("SELECT * FROM messages", function (error, results, fields){
    if(error){
        console.log("test");
    }
    if(results.length > 0) {
        console.log(results);
    }
});

But it doesn't work, it doesn't print anything to console. Running on Linux.

但是它不能工作，它不能打印任何东西来控制台。在Linux上运行。

1 个解决方案

#1

For your particular question, do not put your results in an if statement yet. Do this instead, just to see what you're working with:

对于您的特定问题，不要将结果放在if语句中。这样做，看看你在做什么:

console.log( results.toString() );
console.log( JSON.stringify( results ) ); //sometimes this throws errors, if the object is complex

That should let you see what you're working with. If reulsts isn't an array, it won't have a .length attribute, and you won't reach the console.log.

这会让你知道你在做什么。如果reulsts不是数组，那么它就没有.length属性，您也无法访问console.log。

However...

然而……

I'm always pushing KnexJS when I see raw MySQL statements in Node code. Knex handles two common things for you, db connections and connection pools, plus makes writing dynamic queries a breeze. (as in, you don't have to manipulate SQL strings...)

当我在节点代码中看到原始的MySQL语句时，我总是推KnexJS。Knex为您处理两件常见的事情:db连接和连接池，以及编写动态查询。(比如，您不必操纵SQL字符串……)

Install knex npm install knex --save

安装knex npm安装knex——保存

In your app or environment setup

在你的应用程序或环境设置中。

var Knex = require('knex');
Knex.knex = Knex({...}); //set options for DB

In other files, reference the instance like this:

在其他文件中，引用实例如下:

var knex = require('knex).knex;

So your query could look like this:

你的查询可能是这样的:

var query = knex('messages').select();
console.log('About to perform query: ' + query.toString() );
query.exec( function( err, results ){
    if(error){
        console.log("test");
    }
    console.log(results);
    //do other things here, like callback(results);
} );

Good luck!

好运！

#1