如何在 html 表格单元格中分别显示 group_concat 结果？

Question

关于我之前尚未回答的问题How to group array value duplicate and customize the display of the results of the array in html table?，我选择以其他方式仅显示 5 行。

这是数据库：

 lid   class_id   class         Q1-2      Q3-4      total   item_group  
-----  -------    -----         -----    -----      -----   ----------
   1     73       Leader        5000      50000     10000      33
   1     77       Consultant    4000      4000      8000       33
   1     83       Coordinator   3000      3000      6000       33
   2     73       Leader        10000     10000     20000      33
   2     76       Staff         4000      4000      8000       33
   2     77       Consultant    5000      50000     10000      33
   3     73       Leader        15000     15000     30000      33
   3     78       Team Leader   4000      4000      8000       33

这是我使用的 SQL 查询：

$sql = "SELECT *, group_concat(AZ.lid) as lids, group_concat(AZ.total) AS totals FROM (
    SELECT * FROM view_items WHERE lid='1' 
    UNION 
    SELECT * FROM view_items WHERE lid='2' 
    UNION 
    SELECT * FROM view_items WHERE lid='3' 
) AS AZ WHERE item_group='33' GROUP BY class_id";

这是 SQL 结果：

class id    class        lid    Q1-2    Q3-4     lids    totals             item_group
---------   -----       ------  -----   -----    -----   ------             ----------
   73      Leader         1     5000    5000     1,2,3   10000,20000,30000     33
   77      Consultant     1     4000    4000     1,2     8000,10000            33
   83      Coordinator    1     3000    3000     1       6000                  33
   76      Staff          2                      2       8000                  33
   78      Team Leader    3                      3       8000                  33

$proj_lid->lid is equals to 1 (Displayed in the P1 column only)

$row->lid is equals to 1 (Displayed in the P1 column only)

$limit is 3 (The count of P's)

这是html表格部分：

<?php
 for($iy=1; $iy<=$limit; $iy++){                    
    $sql_lid =  "SELECT * FROM view_items WHERE lid='$iy' GROUP BY lib_id ORDER BY lid ASC";
    $query_lid = $this->db->prepare($sql_lid);
    $query_lid->execute();
    $res=$query_lid->fetch();   
    $lids = $res->lid;
    $lid_arr[] = $lids ;    
    $sql_arr = "";  
    if($iy==1) $sql_arr .= "SELECT *, group_concat(AZ.lid) as lids, group_concat(AZ.total) AS totals FROM (";   
    $sql_arr.="SELECT * FROM view_items WHERE lid='$lids'";   
    if($iy!=$limit) $sql_arr .= " UNION ";      
    if($iy==$limit)  $sql_arr.=" ) AS AZ WHERE item_group='33' GROUP BY class_id";
    $sqlArr[] = $sql_arr;                               
}
 $sql = implode("",$sqlArr);        
 $query = $this->db->prepare($sql);
 $query = $this->db->prepare($sql);
 $query->execute();
 $result = $query->fetchAll();
 foreach($result as $row){  
    if($row->item_group == "33"){                       
        $q1 = ($row->q1-2)
        $q3 = ($row->q3-4) 
        $total = $q1 + $q3;
?>
<tr>            
    <td><?php echo $row->class; ?></td>             
    <td><?php if($q1 != 0 && $proj_li->lid == $row->lid){ echo ($q1 < 0 ? "(".number_format(abs($q1),2).")" : number_format($q1,2));} else{ echo "-";} ?> </td>
    <td><?php if($q3 != 0 && $proj_lid->lid == $row->lid ){ echo ($q3 < 0 ? "(".number_format(abs($q3),2).")" : number_format($q3,2));} else{ echo "-";} ?> </td>               
    <td><?php if($total != 0 && $proj_lid->lid == $row->lid ){ echo ($total < 0 ? "(".number_format(abs($total),2).")" : number_format($total,2));} else{ echo "-";} ?> </td>   
<?php   
    $totals = explode(", ", $row->totals);  
    foreach ($totals as $rowstotals) {      
    }
    for($i = 1; $i <= $limit; $i++){                    
    if ($i != $proj_lid->lid && $proJ-lid->lid < $i){
?>
      <td><?php if($rowstotals != 0){ echo ($rowstotals < 0 ? "(".number_format(abs($rowstotals),2).")" : number_format($rowstotals,2));} else{ echo "-";}?></td>   
<?php
    } else{ } 
   } 
  }  
 } 
?>
</tr>       

我设法显示了预期的输出
预期的输出（只有 5 行，没有重复的类 id）

但是在单独显示 group_concat 值时出现了另一个问题。我需要 P2 和 P3 中的值来仅显示来自 group_concat 的一个结果。

这应该是预期的输出

更新：我发现（可能）与我想做的类似的输出（忘记了我在哪里看到这个链接） Link

Answer 1

这就是我的想法：

SELECT lid, class_id,class, `Q1-2`,`Q3-4`,total,
       CASE WHEN COUNT(*)>=2 THEN SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(total ORDER BY lid ASC SEPARATOR ' '),' ',2),' ',-1) END AS P2,
       CASE WHEN COUNT(*)>=3 THEN SUBSTRING_INDEX(SUBSTRING_INDEX(GROUP_CONCAT(total ORDER BY lid ASC SEPARATOR ' '),' ',3),' ',-1) END AS P3
      FROM (SELECT * FROM view_items WHERE lid='1' UNION 
            SELECT * FROM view_items WHERE lid='2' UNION 
            SELECT * FROM view_items WHERE lid='3' ) AS AZ 
      WHERE item_group='33'
GROUP BY class_id ORDER BY lid ASC;

我在GROUP_CONCAT 值上使用了两次SUBSTRING_INDEX 函数，该值等于或大于2，但在此示例中，我停在了3 个计数处。我还在GROUP_CONCAT 中添加了ORDER BY lid ASC，以确保它将返回由lid 排序的值。