我有一个数据库，其表名为from datetime import date
from datetime import datetime
import pandas as pd
import sqlite3
import numpy as np
from sqlalchemy import create_engine
engine = create_engine('sqlite:///C:\\\\\data3.db', echo=False)
#create_local table()
name = 'Bob'
startDate = pd.to_datetime('10/02/2019').date()
endDate = pd.to_datetime('10/09/2019').date()
d = pd.date_range(start=startDate, end=endDate, freq='D')
dd = pd.DataFrame({'Date': d, 'Name':[name]*len(d)})
#print (dd)
df1 = pd.DataFrame(dd, columns =['Date'])
# PUll data from database
dates= {'Date':['2019-10-07','2019-10-06','2019-11-03','2019-11-02','2019-10-09','2019-10-08','2019-10-07','2019-10-06','2019-10-05','2019-10-04','2019-10-03','2019-10-02']}
df=pd.DataFrame(dates)
df['Date']=df['Date'].astype(str)
df['Date']=df['Date'].str.slice(0,10)
#create column and count
df2 = pd.DataFrame(df, columns = ['Date'])
df2= df2.groupby("Date").agg({"Date": np.sum, "Date": pd.Series.count}).rename(columns={'Date': 'count'})
# extract the dates with 2 counts into new dataframe
df2=df2.loc[df2['count'] == 2]
print (df2)
，列为Users，username。我想基于sum_score检索会话用户的等级。所以我尝试了类似下面的代码：
sum_score我要打印<?php
session_start();
$db = mysqli_connect('localhost', 'root', '', 'registration');
$rankname= $_SESSION['username'];
?>
<body>
<?php
$selectrank = "SELECT username, FIND_IN_SET(sum_score, (SELECT GROUP_CONCAT( sum_score ORDER BY sum_score DESC ) FROM users )) AS rank FROM users WHERE username = '$rankname'";
$selectuserrank= mysqli_query($db,$selectrank);
$ranking= mysqli_fetch_assoc($selectuserrank)
?>
Your rank is #<?php echo "$ranking"; ?>
的等级。但是使用上面的代码我得到了错误
数组到字符串的转换
在session_user
有人可以告诉我如何获得排名。
答案 0 :(得分：0)
这意味着$ranking是一个数组。首先，通过print_r($ranking)查看此数组。然后选择所需的元素，在您的情况下为rank
所以，写下：
<?php echo $ranking['rank']; ?>
不仅仅是<?php echo $ranking; ?>