Question

我有一个查询，我想在我的WHERE条件下使用ALIASED列过滤结果集，我读到您不能执行此操作，但是我还没有另一种有效的方法，因为我正在处理成千上万条记录。

$str = "SELECT
                mainclass.id AS classid,
                mainclass.code AS classcode,
                Sum(CASE WHEN enroll.acctok = '1' AND enroll.assessed = '1'
                    THEN enroll.assessed 
                    ELSE 0 end) AS assessedinclass,
                Sum(enroll.validated = '1') AS validatedinclass,
                section.name AS sectionname,
                subject.code AS subcode,
                subject.subdesc,
                mainclass.units,
                sched.name AS schedule,
                mainclass.tutorial,
                mainclass.dissolved,
                mainclass.slots,
                mainclass.ismother,
                mergeclass.code AS mothercode,
                mergeclass.id AS mothercodeid,
                mergeclass.slots AS mothercodeslots,
                mainclass.mergein,
                mainclass.inst,
                instructor.lname,
                instructor.fname,
                instructor.mname,
                instructor.suffix
            FROM
                class AS mainclass
                Left Join enrolldet ON mainclass.id = enrolldet.class
                Left Join enroll ON enrolldet.enrollno = enroll.enrollno
                Inner Join period ON mainclass.period = period.id
                Inner Join section ON mainclass.section = section.id
                Inner Join subject ON mainclass.subject = subject.id
                Left Join sched ON mainclass.sched = sched.id
                Left Join class AS mergeclass ON mainclass.mergein = mergeclass.id
                Left Join instructor ON mainclass.inst = instructor.userid
                Left Join course ON section.course = course.id
             WHERE 
                (period.id = :period OR period.code = :period)";
    if($level != ''){
        $str .= " AND course.level = '".$level."'";
    }
    if($dept != ''){
        $str .= " AND course.dept = '".$dept."'";
    }
    if($display != ''){
        switch ($display) {
            case 'open':
                $str .= " AND mainclass.slots > assessedinclass";
                break;
            case 'dissolved':
                $str .= " AND mainclass.dissolved = 1";
                break;
            case 'tutorial':
                $str .= " AND mainclass.tutorial = 1";
                break;
            case 'closed':
                $str .= " AND mainclass.slots <= assessedinclass";
                break;
        }       
    }            
    $str .= "GROUP BY
                mainclass.id,
                mainclass.code";
    $str .= " ORDER BY subject.code, mainclass.id";
    return $this->_db->select($str,array(':period' => $period));

im尝试使用ASSESSEDINCLASS WHERE mainclass.slots进行过滤> ASSESSEDINCLASS表示主题已打开

而如果mainclass.slots <= ASSESSEDINCLASS，它将被视为已关闭

Answer 1

您可以在下面尝试。编写一个外部选择，其中将包含所有必需的列供您处理过滤器。

select
    classid,
    classcode,
    assessedinclass,
    validatedinclass,
    sectionname,
    subcode,
    subdesc,
    units,
    schedule,
    tutorial,
    dissolved,
    slots,
    ismother,
    mothercode,
    mothercodeid,
    mothercodeslots,
    mergein,
    inst,
    lname,
    fname,
    mname,
    suffix 
from 
    (select
         mainclass.id AS classid,
         mainclass.code AS classcode,
         Sum(case when enroll.acctok = '1' and enroll.assessed = '1'
                    then enroll.assessed 
                    else 0 
             end) as assessedinclass,
         Sum(enroll.validated = '1') AS validatedinclass,
         section.name AS sectionname,
         subject.code AS subcode,
         subject.subdesc,
         mainclass.units,
         sched.name AS schedule,
         mainclass.tutorial,
         mainclass.dissolved,
         mainclass.slots,
         mainclass.ismother,
         mergeclass.code AS mothercode,
         mergeclass.id AS mothercodeid,
         mergeclass.slots AS mothercodeslots,
         mainclass.mergein,
         mainclass.inst,
         instructor.lname,
         instructor.fname,
         instructor.mname,
         instructor.suffix
     from
         class as mainclass
     left join 
         enrolldet on mainclass.id = enrolldet.class
     left join 
         enroll on enrolldet.enrollno = enroll.enrollno
     inner join 
         period on mainclass.period = period.id
     inner join 
         section on mainclass.section = section.id
     inner join 
         subject on mainclass.subject = subject.id
     left join 
         sched on mainclass.sched = sched.id
     left join 
         class as mergeclass on mainclass.mergein = mergeclass.id
     left join 
         instructor on mainclass.inst = instructor.userid
     left join 
         course on section.course = course.id)
where
    (period.id = :period OR period.code = :period);

您的最终查询将是-

select
    <req_cols> 
 from
     (select 
          <agg_cols> 
      from 
          table 
      group by 
          <grpCols>)
where 
    <filter on agg cols>

Answer 2

$str = "SELECT
            mainclass.id AS classid,
            mainclass.code AS classcode,
            Sum(CASE WHEN enroll.acctok = '1' AND enroll.assessed = '1'
                THEN enroll.assessed 
                ELSE 0 end) AS assessedinclass,
            Sum(enroll.validated = '1') AS validatedinclass,
            section.name AS sectionname,
            subject.code AS subcode,
            subject.subdesc,
            mainclass.units,
            sched.name AS schedule,
            mainclass.tutorial,
            mainclass.dissolved,
            mainclass.slots,
            mainclass.ismother,
            mergeclass.code AS mothercode,
            mergeclass.id AS mothercodeid,
            mergeclass.slots AS mothercodeslots,
            mainclass.mergein,
            mainclass.inst,
            instructor.lname,
            instructor.fname,
            instructor.mname,
            instructor.suffix
        FROM
            class AS mainclass
            Left Join enrolldet ON mainclass.id = enrolldet.class
            Left Join enroll ON enrolldet.enrollno = enroll.enrollno
            Inner Join period ON mainclass.period = period.id
            Inner Join section ON mainclass.section = section.id
            Inner Join subject ON mainclass.subject = subject.id
            Left Join sched ON mainclass.sched = sched.id
            Left Join class AS mergeclass ON mainclass.mergein = mergeclass.id
            Left Join instructor ON mainclass.inst = instructor.userid
            Left Join course ON section.course = course.id
         WHERE 
            (period.id = :period OR period.code = :period)";
if($level != ''){
    $str .= " AND course.level = '".$level."'";
}
if($dept != ''){
    $str .= " AND course.dept = '".$dept."'";
}
if($display != ''){
    switch ($display) {
        case 'open':
            $str .= " AND mainclass.slots > assessedinclass";
            break;
        case 'dissolved':
            $str .= " AND mainclass.dissolved = 1";
            break;
        case 'tutorial':
            $str .= " AND mainclass.tutorial = 1";
            break;
        case 'closed':
            $str .= " AND mainclass.slots <= assessedinclass";
            break;
    }       
}            
$str .= "GROUP BY
            mainclass.id,
            mainclass.code";

$str .="HAVING <your condition>";

$str .= " ORDER BY subject.code, mainclass.id";
return $this->_db->select($str,array(':period' => $period));

where子句

2 个答案: