php - 只希望那些事件的结果显示在查询中。 PHP MySQL

Question

我是一名新的 MySQL 和 PHP 编码员...大约 7 年前曾经使用过它，但现在它又落入了我的怀抱。目前，代码会拉动学生进行出勤跟踪，其工作方式如下:

$count = sqlValue("SELECT count(*) FROM `attendance` LEFT JOIN `enrollments` ON attendance.`student_class` = enrollments.id Where enrollments.class='".$class."' AND attendance.date='".$date."'");
    if ($count == 0)
    {       
        $query = "SELECT CONCAT_WS('', `students`.`fname`, ' ', `students`.`lname`)  as `student`, `classes`.`class_name` as class, enrollments.id as eid FROM `students` LEFT JOIN `enrollments` ON students.id = enrollments.student LEFT JOIN `classes` ON classes.id = enrollments.class";
        $query.= " WHERE enrollments.class='".$class."'";
        $query.= " ORDER BY students.id";

        $res   = sql($query, $eo);
        $tbody = '';$ids=array();
        if(db_num_rows($res) > 0)

这很好用，但现在他们只想显示那些“活跃”的。我在数据库中添加了一列并对前端进行编码以将学生标记为活跃。所有这一切都有效，现在我想运行一个只显示活跃学生的查询，然后让我使用一个复选框将他们标记为出现在类(class)中。我尝试了以下方法，但没有用:

$count = sqlValue("SELECT count(*) FROM `attendance` LEFT JOIN `enrollments` ON attendance.`student_class` = enrollments.id Where enrollments.class='".$class."' AND attendance.date='".$date."'");
    if ($count == 0)
    {       
        $query = "SELECT CONCAT_WS('', `students`.`fname`, ' ', `students`.`lname`)  as `student`, `classes`.`class_name` as class, enrollments.id as eid FROM `students` LEFT JOIN `enrollments` ON students.id = enrollments.student LEFT JOIN `classes` ON classes.id = enrollments.class";
        $query.= " WHERE enrollments.class='".$class."'" and enrollments.status <> 'Active';
        $query.= " ORDER BY students.id";

        $res   = sql($query, $eo);
        $tbody = '';$ids=array();
        if(db_num_rows($res) > 0)

它在第 45 行抛出错误，即 $query.= " WHERE enrollments.class='".$class."'" and enrollments.status <> 'Active';行。

结构是

    Table structure for table `enrollments`
--

CREATE TABLE IF NOT EXISTS `enrollments` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `student` int(10) unsigned DEFAULT NULL,
  `class` int(10) unsigned DEFAULT NULL,
  `enrollment_date` date NOT NULL,
  `status` varchar(40) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `student` (`student`),
  KEY `class` (`class`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=109 ;

/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;

Answer 1

"'" 中有一个额外的引号。

该行应为:

     $query.= " WHERE enrollments.class='".$class."' and enrollments.status <> 'Active'";