如何从SELECT查询中返回找到的行数

Question

如何从SELECT查询中返回找到的行数

16

83499 2014-01-29

我编写了一个函数,该函数应该返回在SELECT查询中找到的行数,但它似乎总是返回0或数组.我已经搞混了大约一个小时了,但我仍然无法弄清楚！我确定我做错了什么.

MySQL表

 +--------+-------------+---------------------+
| postid |     ip      |        time         |
+--------+-------------+---------------------+
|   1234 | 192.168.0.1 | 2014-01-29 14:27:02 |
|   5678 | 192.168.0.2 | 2014-01-29 14:27:02 |
+--------+-------------+---------------------+

PHP

 ### Search for IP in database
function postviews_get_ip($id, $ip) {
    global $post, $wpdb;

    $wpdb->get_results("SELECT * FROM $wpdb->wp_postviews_ips WHERE postid = $id AND ip = $ip");

    $rowcount = $wpdb->num_rows;

    return $rowcount;
}

postviews_get_ip($id, $_SERVER['REMOTE_ADDR']);
//both $id and $_SERVER['REMOTE_ADDR']) return the values I'm searching for in the database

I wrote a function which is supposed to return the number of rows found in a SELECT query but it always either seems to return 0 or an array. I have been messing around with this for about an hour now and I still can't figure it out! I'm sure I'm doing something stupidly wrong.

The MySQL Table

+--------+-------------+---------------------+
| postid |     ip      |        time         |
+--------+-------------+---------------------+
|   1234 | 192.168.0.1 | 2014-01-29 14:27:02 |
|   5678 | 192.168.0.2 | 2014-01-29 14:27:02 |
+--------+-------------+---------------------+

PHP

### Search for IP in database
function postviews_get_ip($id, $ip) {
    global $post, $wpdb;

    $wpdb->get_results("SELECT * FROM $wpdb->wp_postviews_ips WHERE postid = $id AND ip = $ip");

    $rowcount = $wpdb->num_rows;

    return $rowcount;
}

postviews_get_ip($id, $_SERVER['REMOTE_ADDR']);
//both $id and $_SERVER['REMOTE_ADDR']) return the values I'm searching for in the database

原文
Swen

- 表的名称和表前缀是什么?
  
  What is the name of the table and the table prefix?
  - 0
  - 2014-01-29
  - Chittaranjan
- @Chittaranjan表名称是wp_postviews_ips,不过我不确定您由表前缀表示的含义.
  
  @Chittaranjan Table name is wp_postviews_ips, I'm not sure what you mean by table prefix though.
  - 0
  - 2014-01-29
  - Swen
- 从$ wpdb-> wp_postviews_ips中删除" $ wpdb->"似乎可以解决问题！
  
  Removing "$wpdb->" from $wpdb->wp_postviews_ips seemed to do the trick!
  - 0
  - 2014-01-29
  - Swen
- 这就是我要求输入表名和前缀的原因.所有wordpress表都有一个前缀,您可以在设置wordpress网站时设置该前缀.以下是有关[codex]的更多详细信息(http://codex.wordpress.org/Creating_Tables_with_Plugins#Database_Table_Prefix)请使用正确的表名检查我更新的答案.
  
  That's the reason I had asked for the table name and prefix. All wordpress tables have a prefix which you set during setting up the wordpress site. Here are more details on [codex](http://codex.wordpress.org/Creating_Tables_with_Plugins#Database_Table_Prefix) Please check my updated answer with correct use of table name.
  - 0
  - 2014-01-29
  - Chittaranjan

2 个回答

投票数

- 2
- 2014-01-29
似乎查询是错误的.$ip是字符串,因此您应该在下面加上单引号

$wpdb->get_results("SELECT * FROM {$wpdb->prefix}postviews_ips WHERE postid = $id AND ip = '$ip'");
Seems the query is wrong. $ip is string so you should put single quote around that as below

$wpdb->get_results("SELECT * FROM {$wpdb->prefix}postviews_ips WHERE postid = $id AND ip = '$ip'");
- 尝试过此方法,但仍返回0.
  
  Tried this and it still returns 0.
  - 0
  - 2014-01-29
  - Swen

eteich · Accepted Answer · 2014-01-29

29

2014-01-29

如果您只是想获取计数,则在您的sql中使用$wpdb->get_var();以及使用COUNT()会更好:/p>

 ### Search for IP in database
function postviews_get_ip($id, $ip) {
    global $post, $wpdb;

    $rowcount = $wpdb->get_var("SELECT COUNT(*) FROM $wpdb->wp_postviews_ips WHERE postid = $id AND ip = '$ip'");

    return $rowcount;
}

postviews_get_ip($id, $_SERVER['REMOTE_ADDR']);
//both $id and $_SERVER['REMOTE_ADDR']) return the values I'm searching for in the database

关于上一个示例中出了什么问题,您没有将$wpdb->get_results()实例分配给变量,并且没有它,则没有$wpdb->num_rows;只会返回零,因为它实际上不是从查询实例中拉出,而是全局的$ wbdb对象.

如果您确实想使用get_results():

 ### Search for IP in database
function postviews_get_ip($id, $ip) {
    global $post, $wpdb;

    $ipquery= $wpdb->get_results("SELECT * FROM $wpdb->wp_postviews_ips WHERE postid = $id AND ip = '$ip'");
    $rowcount = $ipquery->num_rows;
    return $rowcount;
}

postviews_get_ip($id, $_SERVER['REMOTE_ADDR']);
//both $id and $_SERVER['REMOTE_ADDR']) return the values I'm searching for in the database

但是除非您需要结果,否则我不会认为需要这样做,在这种情况下,我只返回$ipquery对象并在其上使用num_rows我需要它:

 ### Search for IP in database
function postviews_get_ip($id, $ip) {
    global $post, $wpdb;

    $ipquery = $wpdb->get_results("SELECT * FROM $wpdb->wp_postviews_ips WHERE postid = $id AND ip = '$ip'");
    return $ipquery;
}

$someVariable = postviews_get_ip($id, $_SERVER['REMOTE_ADDR']);
//both $id and $_SERVER['REMOTE_ADDR']) return the values I'm searching for in the database

echo $someVariable->num_rows;

If you are merely trying to get a count, $wpdb->get_var(); along with using COUNT() in your sql will be better:

### Search for IP in database
function postviews_get_ip($id, $ip) {
    global $post, $wpdb;

    $rowcount = $wpdb->get_var("SELECT COUNT(*) FROM $wpdb->wp_postviews_ips WHERE postid = $id AND ip = '$ip'");

    return $rowcount;
}

postviews_get_ip($id, $_SERVER['REMOTE_ADDR']);
//both $id and $_SERVER['REMOTE_ADDR']) return the values I'm searching for in the database

As to what went wrong in your previous example, you weren't assigning your $wpdb->get_results() instance to a variable, and without it $wpdb->num_rows; is just going to return zero as it isn't actually pulling from the instance of the query, but rather the global $wbdb object.

If you do want to use get_results():

### Search for IP in database
function postviews_get_ip($id, $ip) {
    global $post, $wpdb;

    $ipquery= $wpdb->get_results("SELECT * FROM $wpdb->wp_postviews_ips WHERE postid = $id AND ip = '$ip'");
    $rowcount = $ipquery->num_rows;
    return $rowcount;
}

postviews_get_ip($id, $_SERVER['REMOTE_ADDR']);
//both $id and $_SERVER['REMOTE_ADDR']) return the values I'm searching for in the database

But I wouldn't see the need for that unless you needed the results, in which case I would just return the $ipquery object and use num_rows on it when I needed it:

### Search for IP in database
function postviews_get_ip($id, $ip) {
    global $post, $wpdb;

    $ipquery = $wpdb->get_results("SELECT * FROM $wpdb->wp_postviews_ips WHERE postid = $id AND ip = '$ip'");
    return $ipquery;
}

$someVariable = postviews_get_ip($id, $_SERVER['REMOTE_ADDR']);
//both $id and $_SERVER['REMOTE_ADDR']) return the values I'm searching for in the database

echo $someVariable->num_rows;

小加成.执行任何查询以防止SQL注入时,应始终使用prepare(https://developer.wordpress.org/reference/classes/wpdb/prepare/).

Small addition. You should always use prepare (https://developer.wordpress.org/reference/classes/wpdb/prepare/) when executing any queries to prevent sql injection.
- 1
- 2019-05-29
- Maciej Paprocki
实际上,这不应该是一个很小的补充,这很重要,不要使您的代码可通过sql注入进行利用.

Actually that shouldnt be a small addition, that's very important not to make your code exploitable via sql injection.
- 0
- 2019-09-12
- Max Carroll