Laravel：检查 MySQL 查询是否有结果
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Laravel: Check if MySQL query has result
提问by Feralheart
First Laravel project. I have a controllerfunction what checks if there any record with that barcode. If no insert a record. If yes add one for the count.
第一个 Laravel 项目。我有一个控制器功能，用于检查是否有任何带有该条形码的记录。如果没有插入记录。如果是，则为计数加一。
public function sellmode(Request $request){
$barcode=$request->barcode;
$test = DB::select('select count from sellmode where barcode = ?', [$barcode]);
$row_cnt = mysqli_num_rows($test);
if ($row_cnt == 0) {
Debugbar::info('új sor');
DB::insert('insert into sellmode (barcode, count) VALUES (?, ?)', [$barcode, '1']);
} else {
Debugbar::info('Meglév? frissítése');
DB::update('update sellmode set count = count + 1 WHERE barcode = ?' [$barcode]);
}
return view(sell);
}
}
When I tried it, it had the following error:
当我尝试它时，它有以下错误：
ErrorException in SellController.php line 17: mysqli_num_rows() expects parameter 1 to be mysqli_result, array given
SellController.php 第 17 行中的 ErrorException：mysqli_num_rows() 期望参数 1 为 mysqli_result，给定数组
What did I wrong?
我做错了什么？
回答by Jerodev
You can't just just mysql_num_rowson a Laravel query builder. Laravel query builder will return a collection, so you can just use the isEmptyfunction to find out if it has any results.
你不能只mysql_num_rows在 Laravel 查询构建器上。Laravel 查询生成器将返回一个集合，因此您可以使用该isEmpty函数来查看它是否有任何结果。
if ($test->isEmpty()) {
Debugbar::info('új sor');
DB::insert('insert into sellmode (barcode, count) VALUES (?, ?)', [$barcode, '1']);
} else {
Debugbar::info('Meglév? frissítése');
DB::update('update sellmode set count = count + 1 WHERE barcode = ?' [$barcode]);
}
If you are using a Laravel version pre-5.3, the query builder will return an array. In this case, you can use the php countfunction on this array to know how many rows are returned
如果您使用的是 Laravel 5.3 之前的版本，则查询构建器将返回一个数组。在这种情况下，你可以count在这个数组上使用php函数来知道返回了多少行
if (count($test) === 0) {
Debugbar::info('új sor');
DB::insert('insert into sellmode (barcode, count) VALUES (?, ?)', [$barcode, '1']);
} else {
Debugbar::info('Meglév? frissítése');
DB::update('update sellmode set count = count + 1 WHERE barcode = ?' [$barcode]);
}
回答by Ulrik McArdle
It would be a good idea to create a model and use that to query the db. Maybe something like this (in my opinion it is way easier):
创建一个模型并使用它来查询数据库是个好主意。也许是这样的（在我看来它更容易）：
$sellMode = SellMode::where('barcode', $barcode)->get();
if($sellMode->isEmpty()){
Debugbar::info('új sor');
$sellMode = SellMode::create(['barcode' => $barcode, 'count' => 1]);
}
else{
Debugbar::info('Meglév? frissítése');
$sellMode->increment('count');
}
回答by user8128167
When I used test->isEmpty()or count($test) == 0I still kept getting this error:
当我使用test->isEmpty()或count($test) == 0我仍然不断收到此错误时：
Undefined offset: 0
未定义的偏移量：0
So I ended up using this to check for an empty return value from DB::select:
所以我最终使用它来检查来自 DB::select 的空返回值：
$test = DB::select('select count from sellmode where barcode = ?', [$barcode]);
if(collect($test)->first()) {
// ...
} else {
$response = new \stdClass();
$response->error = true;
$response->message = 'Sellmode not found';
return response(json_encode($response))->header('Content-Type','application/json');
}
