当我尝试使用 SELECT COUNT(*) 函数来计算 table 有条件的行时，显示语法错误？

Question

我正在使用这个代码>>>

$recipe_counting    =   $wpdb->get_var( 

            "SELECT COUNT(*)
            FROM '" . $wpdb->prefix . "recipe_ratings'
            WHERE recipe_id ='" . $post_ID . "' AND user_ip='" . $user_IP . "'"

         );

在浏览器开发人员工具的“网络”选项卡中，当我尝试检查我的输出时显示此错误。

<div id="error"><p class="wpdberror"><strong>WordPress database error:</strong> [You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near &#039;&#039;pr4_recipe_ratings&#039;
            where recipe_id =&#039;104&#039; and user_ip=&#039;::1&#039;&#039; at line 2]<br /><code>SELECT COUNT(*)
            from &#039;pr4_recipe_ratings&#039;
            where recipe_id =&#039;104&#039; and user_ip=&#039;::1&#039;</code></p></div>{"status":2}

Answer 1

您可能会尝试删除包含您的表名的 '，因为数据库引擎可以理解您针对字符串创建 SELECT。

SELECT 语句 (https://mariadb.com/kb/en/select/) 的 mariadb 文档提到使用反字符 ` 来引用表名，而不是单引号。

You can quote column names using backticks. If you are qualifying column >names with table names, quote each part separately as >`tbl_name`.`col_name`.

您的查询如下 SELECT COUNT(*) from pr4_recipe_ratings where recipe_id ='104' and user_ip='::1'

当我尝试使用 SELECT COUNT(*) 函数来计算 table 有条件的行时，显示语法错误？

Showing me a syntax error while I am trying to using the SELECT COUNT(*) function to count table rows with conditions?

database

wordpress

select

function

count