How to Use Query Builder In Laravel?

Query Builder is a feature in Laravel that allows you to perform database queries using a fluent syntax instead of writing raw SQL queries. To use Query Builder in Laravel, you can use the query builder methods provided by the framework to build your query.

To use Query Builder, you first need to get an instance of the query builder object by using the DB facade. For example:

$query = DB::table('users');

You can then chain query builder methods to build your query. For example, you can use the where() method to add a WHERE clause to your query:

$query->where('id', 1);

You can also use other query builder methods such as select(), orderBy(), limit() etc. to customize your query further.

Once you have built your query, you can execute it using the get() method to retrieve the results:

$results = $query->get();

You can also use other query builder methods such as first(), find(), count() etc. to retrieve specific results from your query.

Overall, Query Builder in Laravel provides a convenient way to build and execute database queries using a fluent syntax, making it easier to work with databases in your Laravel applications.

What are the different methods available in Laravel Query Builder?

1. Select method: Used to retrieve data from the database table.
2. Insert method: Used to insert data into a database table.
3. Update method: Used to update existing data in a database table.
4. Delete method: Used to delete data from a database table.
5. Where method: Used to filter data based on specific conditions.
6. OrderBy method: Used to sort data in ascending or descending order.
7. GroupBy method: Used to group data based on a specific column.
8. Limit method: Used to limit the number of results returned from a query.
9. Join method: Used to join multiple tables together in a query.
10. Having method: Used to filter data after groupings have been applied.

What is the role of the first method in Laravel Query Builder?

The first method in Laravel Query Builder is used to retrieve the first result from a query. It is often used when you only need to retrieve a single record from a database table. The first method returns an instance of the object representing the record, or null if no matching record is found. It is commonly used in conjunction with other query builder methods to filter and retrieve specific data from a database.

How to perform aggregate functions using Laravel Query Builder?

To perform aggregate functions using Laravel Query Builder, you can use the selectRaw() method along with the desired aggregate function. Here's an example of how you can perform aggregate functions using Laravel Query Builder:

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use Illuminate\Support\Facades\DB;

$totalUsers = DB::table('users')->count(); // Count the total number of users

$averageAge = DB::table('users')->avg('age'); // Calculate the average age of users

$highestSalary = DB::table('employees')->max('salary'); // Find the highest salary among employees

$lowestPrice = DB::table('products')->min('price'); // Find the lowest price among products

You can also use the selectRaw() method to perform more complex aggregate functions like:

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$customAggregate = DB::table('sales')
    ->selectRaw('SUM(revenue) as total_revenue, AVG(quantity) as avg_quantity')
    ->where('date', '>=', '2021-01-01')
    ->get();

This will calculate the total revenue and average quantity of sales where the date is greater than or equal to '2021-01-01'.

Remember to use appropriate table names and column names in your queries. You can explore more aggregate functions and methods available in Laravel Query Builder documentation: https://laravel.com/docs/8.x/queries#aggregates

How to execute a raw SQL query using Laravel Query Builder?

You can execute a raw SQL query using Laravel Query Builder by using the DB facade. Here is an example on how to do this:

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use Illuminate\Support\Facades\DB;

$query = "SELECT * FROM users WHERE id = :id";
$users = DB::select($query, ['id' => 1]);

foreach ($users as $user) {
    // process each user object
}

In this example, we are selecting all fields from the users table where the id is equal to 1. The DB::select() method takes the raw SQL query as the first parameter and an array of bindings as the second parameter. The bindings array is used to bind the values to any placeholders in the query.

You can also use the DB::statement() method to execute a raw SQL query that does not return any results:

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$query = "DELETE FROM users WHERE id = :id";
DB::statement($query, ['id' => 1]);

Remember to be cautious when using raw SQL queries as they can make your application vulnerable to SQL injection attacks. It's a good practice to use Laravel's query builder methods whenever possible to ensure your queries are properly sanitized.