Question

我试图将以下查询结果限制为仅排在前10位的回复。到目前为止，查询完全符合我的要求 - 即它按顺序提供顶级系统列表，按降序排列。我得到了所有31个回复，但我只想要前10个回复。我尝试过创建一个While Do / End While循环，但我无法确切地知道将它放在以下代码中的位置：

$sql = "
SELECT HelpDesk
     , COUNT(*) as NumSys 
  FROM `systems_17-18` 
 WHERE HelpDesk <>'' 
   AND HelpDesk <> 'NONE'    
 GROUP BY HelpDesk 
 ORDER 
    by NumSys DESC
";
$result = $conn->query($sql);
$mycount = 0;
if ($result->num_rows > 0) {
// output data of each row
echo "<table class='uk-table uk-table-condensed uk-table-hover uk-table-striped'>";        
while($row = $result->fetch_assoc()) 
{
$mycount ++;

echo "<tr>" ;
    echo "<td>";

    echo "<a href=" . $row['webaddress'] . " >";
    echo $row['SchoolDistrict'] . "</a>";
    echo "</td><td># " . $mycount . " " . $row['HelpDesk'] . " used by " .  $row[NumSys] . " district(s)";
echo "</td></tr>";
}

echo "</table>";
}

（注意：上面的代码正确地生成了下面的数据。但是，如何将列表限制为仅排在前10位的响应？使用While EndWhile循环？）

加州的学区使用各种帮助台系统：

 1 MyTechDesk used by 52 district(s)
 2 SchoolDude used by 40 district(s)
 3 WebHelpDesk used by 29 district(s)
 4 ZenDesk used by 15 district(s)
 5 SpiceWorks used by 14 district(s)
 6 KACE1000/2000 used by 13 district(s)
 7 FreshDesk used by 8 district(s)
 8 Track-IT! used by 6 district(s)
 9 Custom used by 6 district(s)
10 HEAT (Help Desk) used by 6 district(s)
11 SysAid used by 5 district(s)
12 ServiceDeskPlus used by 4 district(s)
13 GroupLink HelpDesk used by 4 district(s)
14 Altiris used by 4 district(s)
15 GLPI used by 3 district(s)
16 HESK used by 3 district(s)
17 HelpDesk used by 2 district(s)
18 Cherwell used by 2 district(s)
19 OPRAS used by 2 district(s)
20 Manage Engine Service Desk used by 2 district(s)
21 Samanage used by 1 district(s)
22 Absolute used by 1 district(s)
23 OTRS used by 1 district(s)
24 SherpaDesk used by 1 district(s)
25 Applied HelpDesk used by 1 district(s)
26 Public School Works used by 1 district(s)
27 iTop used by 1 district(s)
28 Connectwise used by 1 district(s)
29 Asana used by 1 district(s)
30 RT/SRTS used by 1 district(s)
31 OSTicket used by 1 district(s)

Answer 1

在LIMIT 10声明之后添加ORDER BY。

$sql = "SELECT HelpDesk, COUNT(*) as NumSys FROM `schoolt7_systems`.`systems_17-18` WHERE HelpDesk <>'' AND HelpDesk <> 'NONE'     GROUP BY HelpDesk ORDER by NumSys DESC LIMIT 10";

编辑：从MS SQL Server更改为MySQL

参考：https://www.w3schools.com/sql/sql_top.asp

Answer 2

使用LIMIT：

SELECT
    HelpDesk,
    COUNT(*) AS NumSys
FROM `schoolt7_systems`.`systems_17-18`
WHERE
    HelpDesk <>'' AND
    HelpDesk <> 'NONE'
GROUP BY   
     HelpDesk
ORDER by NumSys DESC
LIMIT 10               -- add this to your query

将查询结果限制在mysql的前10位

2 个答案: