Question

所以我试图找回喜欢的列表。这是我的代码

//Echo total likes of #68
$stmt1 = $con->prepare("SELECT COUNT(*) FROM likes WHERE liked_post_id = :id;");
$stmt1->bindValue(':id', $id, PDO::PARAM_STR);
$stmt1->execute();
$count = $stmt1->rowCount();
echo $count;

我认为这会让所有人都喜欢。但我只得到1回归。这是结构

+-----------------+------------------+------+-----+---------+----------------+
| Field           | Type             | Null | Key | Default | Extra          |
+-----------------+------------------+------+-----+---------+----------------+
| id              | int(11) unsigned | NO   | PRI | NULL    | auto_increment |
| liked_post_id   | varchar(255)     | YES  |     | NULL    |                |
| liked_post_user | varchar(255)     | YES  |     | NULL    |                |
| liked_post_ip   | varchar(255)     | YES  |     | NULL    |                |
+-----------------+------------------+------+-----+---------+----------------+

快速查询

+----+---------------+-----------------+---------------+
| id | liked_post_id | liked_post_user | liked_post_ip |
+----+---------------+-----------------+---------------+
| 77 | 68            | alex            | 127.0.0.1     |
| 78 | 68            | andrew          | 127.0.0.1     |
+----+---------------+-----------------+---------------+

因为我希望得到1，而不是获得2，因为有两个用户喜欢它。有任何想法吗？我也没有收到任何错误。

Answer 1

这样做：

$stmt1 = $con->prepare("SELECT COUNT(*) AS count FROM likes WHERE liked_post_id = :id;");
$stmt1->bindValue(':id', $id, PDO::PARAM_STR);
$stmt1->execute();
$row = $stmt1->fetch(PDO::FETCH_ASSOC);
echo $row['count'];

查询返回1行，该行的内容是表中匹配行的计数。您需要获取行以读取该值。

Answer 2

COUNT（）是一个聚合函数，因此返回行数作为结果。如果您想获取列表，则应将COUNT（*）替换为*。

SELECT likes.* FROM likes WHERE liked_post_id = :id

Answer 3

这是查询结果（SELECT COUNT(*) FROM likes WHERE liked_post_id = :id;）：

+----------+
| COUNT(*) |
+----------+
| 2        |
+----------+

rowCount();返回返回的行数，SELECT COUNT(*) FROM likes WHERE liked_post_id = :id;只返回1行，一行包含喜欢的行数。

您必须阅读该行的内容或以这种方式SELECT完成SELECT * FROM likes WHERE liked_post_id = :id;。后者的优化程度较低，但是如果要在代码的某些部分进行完整的选择，则可以重用返回的内容，这样就可以减少对数据库的查询。

只返回一条记录

3 个答案: