Detailed introduction to the use of where method in Laravel

Laravel is a powerful PHP web application framework and one of the most popular frameworks. It provides many convenient methods for developers to quickly build web applications.

In Laravel, database operations are very common. One of the important operations is to filter the data in the database. Laravel provides many methods to filter data, one of the most commonly used methods is the where method.

This article will introduce in detail how to use the where method in Laravel, as well as common usage and examples.

1. Overview of where method

Laravel’s where method is used to filter data in the database. It is often used in database query and update operations. The where method can implement a variety of different filtering methods by setting different parameters. For example, you can use the where method to filter out data rows that specify conditions, or you can use the where method to update data rows that meet the conditions.

2. Basic usage of where method

The where method can specify query conditions in different ways. The following are some basic usages:

1. Query by column name

Query by column name is the most common usage. The following is a sample code:

$users = DB::table('users')->where('name', 'John')->get();

The above code queries all row data in the table "users" where the "name" column value is "John".

2. Querying by multiple column names

In some cases, you may need to query multiple columns at the same time. The following is a sample code:

$users = DB::table('users')
                    ->where('name', '=', 'John')
                    ->orWhere('name', '=', 'Jane')
                    ->get();

The above code queries all row data in the table "users" where the "name" column value is "John" or "Jane".

3. Using raw expressions in queries

In some cases, you may need to use raw expressions in queries. For example:

$users = DB::table('users')
                    ->where('name', '=', 'John')
                    ->orWhereRaw('name = ? or name = ?', ['Jane', 'Jim'])
                    ->get();

The above code queries all row data in the table "users" where the "name" column value is "John" or "Jane" or "Jim". The orWhereRaw method here is used to set the original condition.

4. Other comparison operators

In addition to the basic equal to "=" comparison operator, the where method also supports other comparison operators, such as greater than ">" , less than "<", greater than or equal to ">=", less than or equal to "<=", not equal to "!=", etc. The following is some sample code:

// 大于等于
$users = DB::table('users')->where('votes', '>=', 100)->get();

// 小于
$users = DB::table('users')->where('votes', '<', 100)->get();

// 大于等于且小于等于
$users = DB::table('users')->whereBetween('votes', [1, 100])->get();

// 在某几个值之间
$users = DB::table('users')->whereIn('id', [1, 2, 3])->get();

// 不在某几个值之间
$users = DB::table('users')->whereNotIn('id', [1, 2, 3])->get();

// Null值
$users = DB::table('users')->whereNull('updated_at')->get();

// Not Null值
$users = DB::table('users')->whereNotNull('updated_at')->get();

// Exists操作
$users = DB::table('users')
                ->whereExists(function ($query) {
                    $query->select(DB::raw(1))
                          ->from('orders')
                          ->whereRaw('orders.user_id = users.id');
                })
                ->get();

The above sample code shows that the where method can complete various types of filtering operations. 
3. Summary
The where method is a very commonly used method in Laravel. It can be used for a variety of different filtering operations, such as query, insert, update, etc. This article introduces the basic usage of the where method, and also provides several different types of sample code. If you use Laravel to develop web applications, these sample codes will be very useful. 
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