如何選擇字段並在SQL中為每個字段計數？

Question

我有一個名為message的SQL表，我想從表中選擇DISTINCT用戶名，該表將向ID為（$ uid）的收件人發送任何消息，並使用單行查詢為每個發件人選擇COUNT(message) 。

我已經試過這段代碼：

$query="SELECT DISTINCT clientname,user_id,user1pic, COUNT("SELECT id FROM messages WHERE clientname=clientname) AS counted FROM messages WHERE receiver=$uid and status='unread' ";
$messages=mysqli_query($cnx,$query);
while($row=mysqli_fetch_array($cnx,$messages)){

echo '<a class="example" > '.$row['clieenter code herentname'].''.$row['counted'].'</a>' ;}
if(mysqli_num_rows($cnx,$messages)<=0){
    echo '<a class="example" href="#">You Have No Messages</a>' ;
}

Answer 1

請嘗試以下操作：

SELECT 
  clientname,
  user_id,
  user1pic, 
  COUNT(1) AS counted 
FROM 
  messages 
WHERE 
  receiver=:uid 
  and status='unread'
Group by
  clientname,
  user_id,
  user1pic;

我已經用參數占位符替換了內聯PHP變量-請使用參數綁定來避免SQL注入。