laravel db query statement

Laravel is a powerful PHP framework. When developing web applications, Laravel provides many convenient functions, among which the database query function is what developers must master.

This article will introduce commonly used database query statements in Laravel, including basic queries, aggregate queries, conditional queries, and related queries, etc., to help developers better use the Laravel framework for database operations.

1. Basic Query

The most basic query statement in Laravel is the select statement, which is used to query data in the data table. Here is a simple query example:

$users = DB::table('users')->get();

This code gets all the data from the users table and stores the results in the $users variable.

In addition, Laravel also provides some simple query auxiliary functions, for example, getting the first record in the table:

$user = DB::table('users')->first();

Querying specific data columns:

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

Filter data from clauses:

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

2. Aggregation query

In Laravel, aggregate functions are used to query and calculate aggregate values ​​of data tables, such as calculation Maximum value, minimum value, average value, sum, etc. The following are code examples of some common aggregate functions:

Calculate the total number of records:

$count = DB::table('users')->count();

Calculate the maximum value:

$max = DB::table('users')->max('age');

Calculate the average:

$avg = DB::table('users')->avg('age');

Calculate the sum:

$total = DB::table('users')->sum('age');

3. Conditional query

Conditional query in Laravel includes using where statement for conditional matching, using orWhere statement to achieve multi-condition matching, and using whereIn and The orWhereIn statement implements querying the records contained in the specified list. The following are some code examples of conditional queries:

Use where statement to achieve conditional matching:

$users = DB::table('users')
            ->where('name', '=', 'John')
            ->where('age', '>', 25)
            ->get();

Use orWhere statement to achieve multi-condition matching:

$users = DB::table('users')
            ->where('name', '=', 'John')
            ->orWhere('age', '>', 25)
            ->get();

Use whereIn and orWhereIn statements to achieve Query the records contained in the specified list:

$users = DB::table('users')
            ->whereIn('id', [1, 2, 3])
            ->get();

$users = DB::table('users')
            ->orWhereIn('id', [1, 2, 3])
            ->get();

4. Associated query

In Laravel, we can implement associated queries between tables through the join statement. Related queries can be used in many different ways, for example, using innerJoin, leftJoin, rightJoin, etc. The following are some code examples of related queries:

Use innerJoin statement to implement inner join:

$users = DB::table('users')
            ->join('orders', 'users.id', '=', 'orders.user_id')
            ->select('users.name', 'orders.price')
            ->get();

Use leftJoin statement to implement left join:

$users = DB::table('users')
            ->leftJoin('orders', 'users.id', '=', 'orders.user_id')
            ->select('users.name', 'orders.price')
            ->get();

Use rightJoin statement to implement right join:

$users = DB::table('users')
            ->rightJoin('orders', 'users.id', '=', 'orders.user_id')
            ->select('users.name', 'orders.price')
            ->get();

The above is an introduction to commonly used database query statements in Laravel. Developers can use them flexibly according to actual needs to perform database query operations quickly and efficiently. In addition, Laravel also provides other powerful database operation functions, such as transaction processing, paging, database migration, etc. These functions can better help developers manage and maintain the database and improve development efficiency.

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