Question

我的代码应该检索＆＃34; DropsRemaining＆＃34;用户ID（它成功），然后从它检索的数字-1。当检索数据时，它返回该字符串＆＃34; [RowDataPacket {DropsRemaining：5}}＆＃34;但是，DropsRemaining中的代码结尾不是-1，而是将DropsRemaining设置为-1。如果有人可以帮忙解决这个问题，我真的很感激。

＆＃13;

var sql = "SELECT DropsRemaining FROM UserData WHERE DiscordID LIKE " + message.author.id;

var DropCount = [];
connection.query(sql, function (err, result) {
	if (!err)
		setValue(result);
	else
		console.log("No Information For That User Found");
});

function setValue(value) {
	DropCount = value;
	console.log(DropCount);
};
//Remove drop from user
	DropCount = DropCount - 1;
var sql = "UPDATE UserData SET DropsRemaining = " + DropCount + " WHERE DiscordID = " + message.author.id;

＆＃13;

Answer 1

问题是你编写Javascript代码的顺序并不完全是它最终的执行方式。

当您调用connection.query()函数时，下一行代码不一定已经具有该函数的结果。

我建议你看看这个book series，他们对这些特征有很好的解释。

以下代码可能会输出预期的响应。请注意，我嵌套了代码，因此我可以正确控制流程。

    var sql = "SELECT DropsRemaining FROM UserData WHERE DiscordID LIKE " + message.author.id;

    // Get the DropsRemaining
    connection.query(sql, function (err, result) {
        if (!err) {
            // No errors in the query, decrement the Drops
            decrementDrop(result);
        } else {
          console.log("No Information For That User Found");
        }
    });

    function decrementDrop(dropsAvailable) {
        var dropsRemaining = dropsAvailable - 1;
        var updateSql = "UPDATE UserData SET DropsRemaining = " + dropsRemaining + " WHERE DiscordID = " + message.author.id;

        // Update the DropsRemaining column to the dropsRemaining, i.e., decrement the DropsRemaining column value
        connection.query(updateSql, function (err, result) {
            if (!err) {
                console.log("DiscordID = " + message.author.id +" has " + dropsRemaining + " drops remaining")
            } else {
                console.log("Error!");
            }
        });
    }

NodeJS和MYSQL问题

1 个答案: