Php 如何使用forloop和union all按列分组

您好，这是我的查询，我从这个查询中得到了3条记录，我只想要一条记录，我正试图按

studentid

foreach ($gdFinaldata['gdskill'] as $skillId => $skillScore){

$filterQuery .= $union_all. "SELECT stu.student_pid

FROM tbl_students stu LEFT JOIN r_job_invitations jbi ON stu.student_email = jbi.email 

LEFT JOIN r_job_scores jsc  ON jsc.student_id = stu.student_pid 

WHERE job_id = ".$jobID."  AND skill_id = ".$skillId." AND gd_score >= ".$skillScore." ";

$union_all=" UNION ALL ";

} //for ends here

记录将如下所示：

SELECT stu.student_pid FROM tbl_students stu LEFT JOIN r_job_invitations jbi ON stu.student_email = jbi.email LEFT JOIN r_job_scores jsc ON jsc.student_id = stu.student_pid WHERE job_id = 88 AND skill_id = 3 AND gd_score >= 1   
UNION ALL
SELECT stu.student_pid FROM tbl_students stu LEFT JOIN r_job_invitations jbi ON stu.student_email = jbi.email LEFT JOIN r_job_scores jsc ON jsc.student_id = stu.student_pid WHERE job_id = 88  AND skill_id = 63 AND gd_score >= 2   
UNION ALL  
SELECT stu.student_pid FROM tbl_students stu LEFT JOIN r_job_invitations jbi ON stu.student_email = jbi.email LEFT JOIN r_job_scores jsc ON jsc.student_id = stu.student_pid WHERE job_id = 88  AND skill_id = 128 AND gd_score >= 3

$groupby = "GROUP BY student_id";
$filterStudents = $conn->query($filterQuery.$groupby);

在此之后，我想通过以下方法添加组：

SELECT stu.student_pid FROM tbl_students stu LEFT JOIN r_job_invitations jbi ON stu.student_email = jbi.email LEFT JOIN r_job_scores jsc ON jsc.student_id = stu.student_pid WHERE job_id = 88 AND skill_id = 3 AND gd_score >= 1   
UNION ALL
SELECT stu.student_pid FROM tbl_students stu LEFT JOIN r_job_invitations jbi ON stu.student_email = jbi.email LEFT JOIN r_job_scores jsc ON jsc.student_id = stu.student_pid WHERE job_id = 88  AND skill_id = 63 AND gd_score >= 2   
UNION ALL  
SELECT stu.student_pid FROM tbl_students stu LEFT JOIN r_job_invitations jbi ON stu.student_email = jbi.email LEFT JOIN r_job_scores jsc ON jsc.student_id = stu.student_pid WHERE job_id = 88  AND skill_id = 128 AND gd_score >= 3

$groupby = "GROUP BY student_id";
$filterStudents = $conn->query($filterQuery.$groupby);

我的问题仍然是返回3个记录，我想按学生分组

供参考：

---

有几种方法可以做到这一点

• 使用

  union

  而不是

  union all

  ，这将只保留唯一的条目

  select ...
  union
  select ...
  union
  select ...
  

• 如果要保留

  union all

  （为什么？），请在所选内容周围使用括号，并在其后面附加

  groupby

  select student_pid
  ( select student_pid, student_id from ...
  union all
  select student_pid, student_id from ...
  union all
  select student_pid, student_id from ... ) as t
  group by student_id
  

  然后，您的PHP看起来像

  foreach（…）{
  $filterQuery.=$union\u all.“选择stu.student\u pid，jsc.student\u id…”
  // ...
  }
  $outerQuery=“选择学生\u pid（”
  $groupby=“）作为t组按学生id”；
  $filterStudents=$conn->query（$outerQuery.$filterQuery.$groupby）；
  

• 您也可以使用

  distinct

  ，而不是

  分组依据，例如
  
  select distinct student_pid
  ( select student_pid from ...
  union all
  select student_pid from ...
  union all
  select student_pid from ... ) as t
  
  

• 在数组中收集结果，然后使用 尽管这是效率最低的，因为它获取所有条目而不是相关部分

---

是的，您的文件查询应该是。通过grptable从（选择…联合选择…联合选择…）中选择*作为grptable组。学生\u尝试调试时缺少某些内容。。谢谢你的帮助，希望这能起作用。可能是内部查询（$filterQuery）中的附加列，请参阅更新的答案。