如果我有几行具有相同的值，如何从mysql结果中获取单个值

Question

我有一个名为“ employees”的数据库，其值如下：

value1     | value2 | value3
-----------------------------
employee1  |  key1  |  boss1
employee2  |  key2  |  boss1
employee3  |  key3  |  boss1
employee4  |  key4  |  boss2
employee5  |  key5  |  boss2

在php中，我试图遍历结果以获取老板的所有雇员，但是仅获得老板姓名一次，我尝试使用GROUP BY ，但是在循环时，这仅显示第一个条目：

$query = "SELECT * FROM employees WHERE value3 = 'boss1' GROUP BY value3";
$result = $db->query($query);
$foreach ($result as $row) {
    echo $row["value1"] . $row["value2"] . $row["value3"];
}

结果是：

employee1  |  key1  |  boss1

Whitout GROUP BY ，当与foreach循环时，它为每个条目显示一次老板名称

$query = "SELECT * FROM employees WHERE value3 = 'boss1'";
$result = $db->query($query);
foreach ($result as $row) {
    echo $row["value1"] . $row["value2"] . $row["value3"];
}

结果是：

employee1  |  key1  |  boss1
employee2  |  key2  |  boss1
employee3  |  key3  |  boss1

我正在尝试获得如下结果：

boss1
    employee1  |  key1
    employee2  |  key2
    employee3  |  key3

Answer 1

您可以在foreach使用if() ，如下所示：

foreach ($result as $row) {
    $i++;
    if ($i==1) {echo $row["value3"];}
    echo $row["value1"] . $row["value2"];
}

比，您可以得到想要的结果：

boss1
employee1  |  key1
employee2  |  key2
employee3  |  key3

Answer 2

您可以使用GROUP_CONCAT()获取每个boss的value1和values2的comma分隔（默认）列表，如下所示：

SELECT 
  GROUP_CONCAT(e.value1) AS value1,
  GROUP_CONCAT(e.value2) AS value2,
  e.value3 AS boss
FROM employees e
WHERE value3 = 'boss1' 
GROUP BY value3;

这将为您提供类似于boss1东西：

employee1,employee2,employee3 | key1,key2,key3 | boss1

编辑1： As a html list, something like: <ul>boss1 <li>employee1</li> <li>employee2</li> <li>employee3</li> </ul> I don't need the html code, but I need to get the data in a format which I can use as a list in html

SELECT 
  CONCAT('<ul>',GROUP_CONCAT(CONCAT('<li>',e.value1,'<\/li>')),'<\/ul>') AS value1,
  GROUP_CONCAT(e.value2) AS value2,
  e.value3 AS boss
FROM employees e
WHERE value3 = 'boss1' 
GROUP BY value3;

注意 ：-您应该使用服务器端语言来实现。 并使用第一个查询。