[英]PHP & MYSQL: using group by for categories
My database has the following setup 我的数据库具有以下设置
productid | productname | category id
and I want to output them like so: 我想像这样输出它们:
category #1
item 1
item 2
item 3
category #2
item 1
item 2
item 3
I used group by the group them together and that works fine, but I want to loop through each group and display the contents of that group. 我把它们组合在一起使用,并且工作正常,但我想循环遍历每个组并显示该组的内容。 How would I do this?
我该怎么做?
I'd recommend just a simple query to fetch all the rows, sorted by category id. 我建议只是一个简单的查询来获取所有行,按类别ID排序。 Output the category only if its value changes from the previous row.
仅当其值从上一行更改时才输出该类别。
<?php
$stmt = $pdo-> query("SELECT * FROM `myTable` ORDER BY categoryID");
$current_cat = null;
while ($row = $stmt->fetch()) {
if ($row["categoryID"] != $current_cat) {
$current_cat = $row["categoryID"];
echo "Category #{$current_cat}\n";
}
echo $row["productName"] . "\n";
}
?>
This should work: 这应该工作:
$categories = array();
$result= mysql_query("SELECT category_id, product_name FROM `table` GROUP BY `catagory_id` ORDER BY `catagory_id`");
while($row = mysql_fetch_assoc($result)){
$categories[$row['category_id']][] = $row['product_name'];
}
// any type of outout you like
foreach($categories as $key => $category){
echo $key.'<br/>';
foreach($category as $item){
echo $item.'<br/>';
}
}
The output you can style yourself. 您可以自己设计的输出。 You simply add everything into a multidimensional array with the category id as the first level keys.
您只需将所有内容添加到多维数组中,并将类别ID作为第一级键。
EDIT : The resulting array might look like this: 编辑 :结果数组可能如下所示:
$categories = array(
'cateogy_id_1' => array(
1 => 'item_1',
2 => 'item_2',
...
),
'cateogy_id_2' => array(
1 => 'item_1',
2 => 'item_2',
...
),
....
);
What you want is to order them by the category, not group them. 你想要的是按类别订购它们,而不是将它们分组。
SELECT * FROM MyTable
ORDER BY category_id, product_id
When you iterate through the list, just output a new header whenever the category_id changes. 当您遍历列表时,只要category_id更改,只需输出一个新标头。
This approach does not need the data to be sorted by category_id. 此方法不需要按category_id对数据进行排序。
You can use php to group each category together in a nested array. 您可以使用php在嵌套数组中将每个类别组合在一起。 After this, the data can be easily be displayed in a table, passed to a grap/chart library, etc...
在此之后,数据可以轻松地显示在表格中,传递到grap /图表库等...
<?php
$stmt = $pdo-> query("SELECT * FROM myTable ORDER BY categoryID");
$categories = []; //the array to hold the restructured data
//here we group the rows from different categories together
while ($row = $stmt->fetch())
{
//i'm sure most of you will see that these two lines can be performed in one step
$cat = $row["categoryID"]; //category id of current row
$categories[$cat][] = $row; //push row into correct array
}
//and here we output the result
foreach($categories as $current_cat => $catgory_rows)
{
echo "Category #{$current_cat}\n";
foreach($catgory_rows as $row)
{
echo $row["productName"] . "\n";
}
}
?>
The easiest way is probably to pull the list of categories, iterate through and pull their attached products. 最简单的方法可能是拉出类别列表,迭代并拉动其附加产品。 (Ie several queries.)
(即几个查询。)
For instance (pseudocode): 例如(伪代码):
$result = fetch_assoc("SELECT category_id FROM categories"); foreach($result as $row) { echo $row['category_id']; $result2 = fetch_assoc("SELECT product_id FROM products"); foreach($result2 as $row2) { echo $row2['product_id']; } }
If you want to do it all in one query you can do something like: 如果您想在一个查询中完成所有操作,您可以执行以下操作:
$result = fetch_assoc("SELECT product_id, category_id FROM products p JOIN categories c ON p.category_id = c.category_id ORDER BY c.category_id ASC"); $last = null; foreach($result as $row) { # Output the category whenever it changes if($row['category_id'] != last) { echo $row['category_id']; $last = $row['category_id']; } echo $row['item_id']; }
Then you can iterate over the result set and pull out the category name whenever it changes. 然后,您可以迭代结果集,并在更改时提取类别名称。
There may be a more sophisticated, elegant way to write the SQL to do everything before you get it from the database, but I'm not that smart. 在从数据库中获取SQL之前,可能有一种更复杂,更优雅的方式来编写SQL以执行所有操作,但我并不那么聪明。 ;)
;)
Note: Examples use pseudo code. 注意:示例使用伪代码。 I use a mysql abstraction class that works like:
我使用的mysql抽象类的工作方式如下:
$db->query("SELECT stuff"); $db->multi_result(); // returns 2d-associative array
I can then foreach($db->multi_result() as $row)
, which is super lazy and awesome. 然后我可以
foreach($db->multi_result() as $row)
,这是超级懒惰和真棒。
I can post the code for the abstraction layer if you like. 如果你愿意,我可以发布抽象层的代码。
$stmt = $dbConnection->prepare("SELECT exam_id, COUNT(report_id) FROM bug_report GROUP BY exam_id; ");
//$stmt->bind_param('s',$exam_id);
$stmt->execute();
$extract = $stmt->get_result();
$count = $extract->num_rows;
if($count){
while($rows = $extract->fetch_assoc()){
$exam_id = $rows["exam_id"];
switch($exam_id){
case "jee_questions":
$jeeBugCount = $rows["COUNT(report_id)"];
break;
case "gate_questions":
$gateBugCount = $rows["COUNT(report_id)"];
break;
}
}
}
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