这个问题在这里已经有答案了：

我可以在php中混合mysql api吗(4个答案）
两年前关门了。
每当我在phpmyadmin中尝试时，下面的查询都可以正常工作：

SELECT CAST(DATETIME AS DATE), Provider, COUNT(Provider) 
FROM purchases 
GROUP BY CAST(DATETIME AS DATE), Provider 
ORDER BY CAST(DATETIME AS DATE) DESC

然而，当我把它放在php脚本中时，我总是收到一个布尔值：

$sql="SELECT CAST(DATETIME AS DATE), Provider, COUNT(Provider) 
FROM purchases 
GROUP BY CAST(DATETIME AS DATE), Provider 
ORDER BY CAST(DATETIME AS DATE) DESC";

if (mysqli_query($con,$sql))
  {

    $result = mysql_query($sql);
    while($row = mysql_fetch_assoc($result)) {
    echo $row['CAST(DATETIME AS DATE)'];
    echo $row['Provider'];
    echo $row['COUNT(Provider)'];

}

}
else
  {
  echo "Error creating table: " . mysqli_error($con);
  }

mysqli_close($con)

;
我真的很想得到一些关于如何解决这个问题的建议。