我有一个一对多表(实际上应用程序实际上会使用多对多，但这与我的问题无关)。假设两列具有以下值:
c1 c2
2 3
4 1
4 3
4 4
6 4
对于给定的c1值4，我想用数组[1,2,4,6]中的c2值更新表。因此，我的表现在将如下所示(注意，添加了记录4,2和4,6，记录4,3不再存在，记录4,1和4,4保持不变):
c1 c2
2 3
4 1
4 2
4 4
4 6
6 4
实现这一目标的最佳方法是什么?我"可以"首先查询数据库以选择c1=4的现有值，然后使用array_intersect()来识别添加和删除的记录，并根据需要插入/删除，但是，这似乎有些过分。
我知道这是一个古老的问题，但我花了一段时间才找到答案，这个问题在谷歌上排名很高。
我找到了下面的代码并修改了它:
INSERT IGNORE INTO my_table VALUES (1,1), (1,2), (1,3);
DELETE FROM my_table WHERE c1 NOT IN (1,2,3) AND my_table = 1;
源代码来源:http://borzacchiello.it/how-to-update-a-junction-table/
我的代码，我修改使用PHP变量&PDO循环:
$a_id = $my_main_id //this would be c1 in the above question
//Set Variable From Post
$var_1 = isset($_POST['var_1']) ? $_POST['var_1'] : '';
$var_2 = isset($_POST['var_2']) ? $_POST['var_2'] : '';
//etc, etc, etc
//put variables into array
$data = array('var_1'=>$var_1, 'var_2'=>$var_2, 'var_3'=>$var_3, 'var_4'=>$var_4, 'tarp_5'=>$tarp_5);
//get count of variable that contain data and not empty
$data_array_count = 0;
foreach ($data as $column => $value) {
if($value != '') {
$data_array_count = ++$data_array_count;
}
}
//if contains atleast one variable run update code
if($data_array_count != 0) {
//loops through and inserts each varible in array
foreach ($data as $column => $value) {
//ignores variables without any data
if($value != '') {
$insert = $db->prepare("INSERT IGNORE my_table (a_id, b_id) VALUES (:a_id, :b_id)");
$insert->execute(array(':a_id' => $a_id,
':b_id' => $value ));
}
}
//sets up variables in array to remove any records that need to be deleted
$columns = "";
$holders = "";
foreach ($data as $column => $value) {
if($value != '') {
$columns .= ($columns == "") ? "" : ", ";
$columns .= $column;
$holders .= ($holders == "") ? "" : ", ";
$holders .= ":$column";
}
}
$delete = $db->prepare("DELETE FROM my_table WHERE accessory_id NOT IN ($holders) AND (carrier_id = :a_id)");
//bind value for main id
$delete->bindValue(":a_id", $a_id);
//loop to bind value for each variable stored in array with data
foreach($data as $placeholder => $value) {
if($value != '') {
$delete->bindValue(":" . $placeholder, $value);
}
}
$delete->execute();
}
使用原始问题中的示例，您必须为想要更新的每个c1 id号运行此代码(c1相当于我的示例中的$a_id变量)。