Laravel is an excellent web application framework whose flexible structure and rich feature set make it the first choice of many developers. In Laravel, specifying fields means selecting only certain fields, not all fields, when operating the database. This is useful in many situations, for example: if you only care about some data in the table and don't want to query all the data, or if the query results are large and performance needs to be improved.

In this article, we will introduce how to specify fields in Laravel, allowing you to operate the database more flexibly and improve the performance of your application.

1. Use the select() method to specify fields

Laravel’s query builder provides a select() method, Can be used to specify the fields to select. This method accepts one or more parameters, which can be a string containing a comma-separated list of field names to be selected, or multiple strings, each string representing a field to be selected. The following is the sample code for specifying fields using the select() method:

$users?=?DB::table('users')->select('id',?'name',?'email')->get();

In the above example, we passed 'id', 'name in the select() method ', 'email' parameters, indicating that only these three fields in the table are selected. get()The method is used to execute the query and return the query results.

2. Use the $fillable attribute of the model

If you are using Laravel's model (Model), you can use the model's The $fillable attribute specifies the fields to allow bulk assignment. This way, when you call the model's create() or update() method, only the fields specified in the $fillable attribute will be assigned a value. The following is sample code for specifying fields using the $fillable attribute:

class?User?extends?Model
{
????protected?$fillable?=?['name',?'email',?'password'];
}

In the above example, we have specified three fields using the $fillable attribute: name, email and password. If you call the model's create() method and pass the values ??of these three fields, these values ??will be automatically saved to the database.

3. Using the $guarded attribute of the model

In contrast to the $fillable attribute, Laravel's model also provides An attribute named $guarded can be used to specify fields that are not allowed to be changed through bulk assignment. If you specify the $guarded attribute, $ is not included when calling the model's create() or update() method for bulk assignment. The field specified in the guarded attribute. Here is sample code to specify a field using the $guarded attribute:

class?User?extends?Model
{
????protected?$guarded?=?['id',?'created_at',?'updated_at'];
}

In this example, we have specified the id using the $guarded attribute , created_at and updated_at fields, these fields will be excluded during batch assignment.

4. Use the pluck() method to specify a single field

If you only need the value of a single field in the query table, you can use the query builder's pluck()Method. This method accepts a parameter that represents the name of the field you want to query. The following is the sample code for specifying a single field using the pluck() method:

$name?=?DB::table('users')->where('id',?1)->pluck('name');

In the above example, we use the where() method to filter out the A record with id equal to 1, and use the pluck() method to select the value of the name field. This query returns a string containing the value of the specified field.

Summary

The above are the four methods of specifying fields in Laravel. Using the above methods, you can operate the database more flexibly and improve application performance. Regardless of which method you choose, when querying large amounts of data, querying only the fields you need is a good practice and can significantly reduce data transfer volume and query execution time.

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