Node.js返回MySQL查询的结果

I have the following function that gets a hexcode from the database

我有以下函数从数据库中获取十六进制代码

function getColour(username, roomCount)
{
    connection.query('SELECT hexcode FROM colours WHERE precedence = ?', [roomCount], function(err, result)
    {
        if (err) throw err;
        return result[0].hexcode;
    });
}

My problem is that I am returning the result in the callback function but the getColour function doesn't return anything. I want the getColour function to return the value of result[0].hexcode.

我的问题是我在回调函数中返回结果，但getColour函数不返回任何内容。我希望getColour函数返回result [0] .hexcode的值。

At the moment when I called getColour it doesn't return anything

在我调用getColour时，它不会返回任何内容

I've tried doing something like

我尝试过这样的事情

function getColour(username, roomCount)
{
    var colour = '';
    connection.query('SELECT hexcode FROM colours WHERE precedence = ?', [roomCount], function(err, result)
    {
        if (err) throw err;
        colour = result[0].hexcode;
    });
    return colour;
}

but of course the SELECT query has finished by the time return the value in colour

但当然SELECT查询已经完成了返回颜色值的时间

1 个解决方案

#1

You have to do the processing on the results from the db query on a callback only. Just like.

您必须仅在回调上对db查询的结果进行处理。就像。

function getColour(username, roomCount, callback)
{
    connection.query('SELECT hexcode FROM colours WHERE precedence = ?', [roomCount], function(err, result)
    {
        if (err) 
            callback(err,null);
        else
            callback(null,result[0].hexcode);

    });

}

//call Fn for db query with callback
getColour("yourname",4, function(err,data){
        if (err) {
            // error handling code goes here
            console.log("ERROR : ",err);            
        } else {            
            // code to execute on data retrieval
            console.log("result from db is : ",data);   
        }    

});