我正在将序列号插入总是递增一个的表中，但是当同时有多个请求时，它将为不同的请求插入相同的序列号。我正在使用mysql数据库。
我知道我在代码中太早获取最大序列号，并且如果请求是在同一时间发送的，那么它将为两个都获取相同的序列号。完成所有工作后更新序列号是个好主意吗？如果同时为新请求插入一条记录并更新前一个的序列号怎么办？
public function add(){
$session = $this->request->session();
$company_id = $session->read('Admin.company_id');
$emp_id = $session->read('Admin.emp_id');
$user_email_id = $session->read('Admin.email_id');
$employee_name = $session->read('Admin.employee_name');
$conn = ConnectionManager::get('default');
if ($this->request->is('post')) {
try{
$conn->begin();
$department = $this->request->data['department'];
$data = $this->request->data;
if(!array_key_exists('is_requisition_for_contractor', $data)){
$is_requisition_for_contractor = 0;
} else {
$is_requisition_for_contractor = $data['is_requisition_for_contractor'];
}
if(!array_key_exists('is_requisition_for_employee', $data)){
$is_requisition_for_employee = 0;
} else {
$is_requisition_for_employee = $data['is_requisition_for_employee'];
}
if(!array_key_exists('is_boulder_requisition', $data)){
$is_requisition_for_boulder = 0;
} else {
if($data['is_boulder_requisition'] == ''){
$is_requisition_for_boulder = 0;
} else {
$is_requisition_for_boulder = $data['is_boulder_requisition'];
}
}
$is_requisition_for_plant = 0;
if(!array_key_exists('is_plant_requisition', $data)){
$is_requisition_for_plant = 0;
} else {
if($data['is_plant_requisition'] == ''){
$is_requisition_for_plant = 0;
} else {
$is_requisition_for_plant = $data['is_plant_requisition'];
}
}
if(array_key_exists("files",$this->request->data)) {
$files = $this->request->data['files'];
if (count($files)) {
$files_uploading_response = $this->uploadMultipleFiles($files, 'files/requisitions/');
}
}
$last_material_insert_id = '';
if($this->request->data('material_id')[0] == ''){
if($this->request->data('department') == 1){
$type = 1;
} elseif($this->request->data('department') == 3){
$type = 3;
} elseif($this->request->data('department') == 2){
$type = 2;
}
if($this->request->data('department') == 1 || $this->request->data('department') == 3){
$conn->execute("INSERT INTO material (material_name, material_type_id, company_id, status, is_approved_by_admin) VALUES (?,?,?,?,?)",[$this->request->data('material_name'), $type, $company_id, 1,0]);
$last_material_insert_id = $conn->execute("SELECT LAST_INSERT_ID() AS last_id")->fetchAll('assoc');
} elseif($this->request->data('department') == 2) {
//todo for unapproved material
$conn->execute("INSERT INTO material (part_no, material_type_id, company_id, status, is_approved_by_admin,unique_category_id) VALUES (?,?,?,?,?,?)",[$this->request->data('part_no')[0], $type, $company_id, 1,0,$this->request->data('unique_category_id')[0]]);
$last_material_insert_id = $conn->execute("SELECT LAST_INSERT_ID() AS last_id")->fetchAll('assoc');
}
}
// here i am fatching max serial number from table
$requistion_number = $conn->execute("SELECT IF(MAX(requisition_no) IS NULL, 0,MAX(requisition_no)) AS requisition_no FROM requisition WHERE site_id = ?",[$this->request->data('site_id')])->fetchAll('assoc');
$Requisition = TableRegistry::get('requisition');
$requisition = $Requisition->newEntity();
$requisition->registered_on = $this->request->data['date'];
$requisition->department_id = $this->request->data('department');
$requisition->site_id = $this->request->data('site_id');
$requisition->issues_to_id = $this->request->data['prepared_by_id'];
$requisition->prepared_by_id = $this->request->data['prepared_by_id'];
$requisition->approved_by_id = $this->request->data['hod_id'];
$requisition->hod_id = $this->request->data['hod_id'];
$requisition->is_diesel_requisition_for_employee = $is_requisition_for_employee;
$requisition->is_diesel_requisition_for_contractor = $is_requisition_for_contractor;
$requisition->is_requisition_for_boulder = $is_requisition_for_boulder;
$requisition->is_requisition_for_plant = $is_requisition_for_plant;
if(array_key_exists('for_tanker_stock', $this->request->data)) {
$requisition->for_tanker_stock = 1;
}
if($last_material_insert_id != ''){
$requisition->is_material_approved_by_admin = 0;
}
$requisition->status = 1;
$site_id = $this->request->data['site_id'];
$requisition->requisition_no = $requistion_number[0]['requisition_no'] + 1;
$requistionnumber = $requistion_number[0]['requisition_no'] + 1;
$saveRequsition = $Requisition->save($requisition);
$conn->commit();
}
我期望每个请求输出不同的序列号。任何优化方法都可以做到这一点。预先感谢。
答案 0 :(得分：0)
您当前要做的是首先获得旧的申请编号，如下所示：
$requistion_number = $conn->execute("SELECT IF(MAX(requisition_no) IS NULL, 0,MAX(requisition_no)) AS requisition_no
FROM requisition WHERE site_id = ?",[$this->request->data('site_id')])->fetchAll('assoc');
然后增加它，然后再保存并提交。
我的建议是在保存并提交请购单之前根本不设置$requistion_number ，而是在之后确定$requistion_number。
您现在想知道如何？
好吧，您需要计算该申请所针对的站点的表中的申请行总数，然后添加一个，如下所示：
$last_requisition_id = $conn->execute("SELECT LAST_INSERT_ID() AS last_id")->fetchAll('assoc');
$site_id = $this->request->data('site_id');
$requisition_number = $conn->execute("SELECT COUNT(*) AS requisitionsCount
FROM requisition
WHERE <primary_key> <= ? AND
site_id = ?",
[$last_requisition_id, $site_id]) + 1;
$conn->execute("UPDATE requisition
SET requisition_no = ?
WHERE <primary_key> <= ?",
[$requisition_number, $last_requisition_id]);
我知道此代码无法正常工作。 $requisition_number可能包含一个以requisitionsCount作为值的数组，但是您可以对此进行纠正。
由于使用的是数据库表中已经存在的数据，因此不会冒两行将获得相同的$requisition_number的风险。 这里的假设是请购单不会被删除。
答案 1 :(得分：0)
好吧，采用相同的策略，在插入行之后设置$requisition_number（请参阅我的其他答案），但是使用与用于确定新申请编号相同的方法的单个查询：< / p>
$conn->execute("UPDATE requisition
SET requisition_no = (SELECT IF(MAX(requisition_no) IS NULL, 0,MAX(requisition_no)) AS requisition_no FROM requisition WHERE site_id = ?) + 1",
[$this->request->data('site_id')]);
这里的想法是，单个查询将在一个步骤中执行，而不会受到其他类似查询的干扰。