Question

我想在一个查询中执行以下操作：

$query = mysql_query("SELECT name FROM tbl_users WHERE category = '1'");
while($row = mysql_fetch_assoc($query))
{
$query2 = mysql_query("SELECT datecreated 
                       FROM tbl_comments 
                       ORDER BY datecreated DESC LIMIT 1");
$row2 = mysql_fetch_assoc($query2);
echo $row['name'] . " > " . $row2['datecreated'] ."<br />";
}

有一个用户表和一个评论表，我想显示一个用户列表和旁边最后一条评论的日期？

这可以在一个查询中实现吗？

Answer 1

您可以使用以下SQL执行此操作：

SELECT name,
       (
        SELECT datecreated
          FROM tbl_comments
          WHERE tbl_users.user_id = tbl_comments.user_id
          ORDER BY datecreated LIMIT 1
       )
FROM tbl_users
WHERE category = '1';

或使用：

SELECT tbl_users.name, MAX(datecreated) AS latestcomment
  FROM tbl_users LEFT JOIN tbl_comments ON (tbl_users.user_id = tbl_comments.user_id)
  GROUP BY tbl_users.name;

MYSQL喜欢加入但只需要最新的一行？

1 个答案: