Object Oriented Programming with Laravel - Session 6
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Migrations allow a team to modify and share a database schema. The document discusses migrations, seeding test data, and using Eloquent to interact with database tables through models. Eloquent provides an ActiveRecord implementation to query, insert, update and delete records, with conventions like assuming a table name based on the plural model name. The document provides examples of defining models, retrieving, updating and deleting records, along with best practices for large data sets.
Object Oriented Programming with Laravel - Session 6
- 1. Object-Oriented Programming (with Laravel) By: Shahrzad Peyman Session 6 May-2017 [email protected] 1
- 2. 2 Today’s Presentation • DataBase:Migrations • DataBase:Seeding • Eloquent (Getting Start)
- 3. 3 DataBase:Migrations Migrations are like version control for your database, allowing your team to easily modify and share the application's database schema. Migrations are typically paired with Laravel's schema builder to easily build your application's database schema. If you have ever had to tell a teammate to manually add a column to their local database schema, you've faced the problem that database migrations solve.
- 4. Generating Migrations 4 To create a migration, use the make:migration Artisan command: The new migration will be placed in your database/migrations directory. Each migration file name contains a timestamp which allows Laravel to determine the order of the migrations.
- 5. 5 The --table and --create options may also be used to indicate the name of the table and whether the migration will be creating a new table. These options simply pre-fill the generated migration stub file with the specified table. Generating Migrations
- 6. 6 Migration Structure A migration class contains two methods: up and down. The up method is used to add new tables, columns, or indexes to your database, while the down method should simply reverse the operations performed by the up method.
- 7. Running Migrations 7 To run all of your outstanding migrations, execute the migrate Artisan command:
- 8. 8 Rollback & Migrate In Single Command The migrate:refresh command will roll back all of your migrations and then execute the migrate command. This command effectively re-creates your entire database: Running Migrations
- 9. Create Table 9 To create a new database table, use the create method on the Schema facade. The create method accepts two arguments. The first is the name of the table, while the second is a Closure which receives a BluePrint object that may be used to define the new table:
- 10. Tables 10
- 11. Renaming / Dropping Tables 11
- 12. Columns Of course, when creating the table, you may use any of the schema builder's column methods to define the table's columns. 12
- 15. 15 Before modifying a column, be sure to add the doctrine/dbal dependency to your composer.json file. The Doctrine DBAL library is used to determine the current state of the column and create the SQL queries needed to make the specified adjustments to the column: Modifying Columns
- 16. 16 Modifying Columns The change method allows you to modify some existing column types to a new type or modify the column's attributes. For example, you may wish to increase the size of a string column. To see the change method in action, let's increase the size of the name column from 25 to 50:
- 17. Rename/Drop Column 17 Before renaming a column, be sure to add the doctrine/dbal dependency to your composer.json file.
- 18. Indexes 18 The schema builder supports several types of indexes. First, let's look at an example that specifies a column's values should be unique. To create the index, we can simply chain the unique method onto the column definition:
- 19. 19 Indexes You may even pass an array of columns to an index method to create a compound index. Laravel will automatically generate a reasonable index name, but you may pass a second argument to the method to specify the name yourself.
- 20. 20 Foreign Key Constraints Laravel also provides support for creating foreign key constraints, which are used to force referential integrity at the database level. For example, let's define a user_id column on the posts table that references the id column on a users table:
- 21. 21 Drop Foreign Key To drop a foreign key, you may use the dropForeign method. Foreign key constraints use the same naming convention as indexes. So, we will concatenate the table name and the columns in the constraint then suffix the name with "_foreign":
- 22. 22 Database:Seeding Laravel includes a simple method of seeding your database with test data using seed classes. All seed classes are stored in the database/seeds directory. Seed classes may have any name you wish, but probably should follow some sensible convention, such as UserTableSeeder, etc. By default, a databaseSeeder class is defined for you. From this class, you may use the call method to run other seed classes, allowing you to control the seeding order.
- 23. Writing Seeders 23 To generate a seeder, execute the make:seeder Artisan command. All seeders generated by the framework will be placed in the database/seeds directory. A seeder class only contains one method by default: run. This method is called when the db:seed Artisan command is executed. Within the run method, you may insert data into your database however you wish.
- 25. 25 Running Seeders Once you have written your seeder classes, you may use the db:seed Artisan command to seed your database. By default, the db:seed command runs the DatabaseSeeder class, which may be used to call other seed classes. However, you may use the --class option to specify a specific seeder class to run individually: 25
- 26. 26 Eloquent The Eloquent ORM included with Laravel provides a beautiful, simple ActiveRecord implementation for working with your database. Each database table has a corresponding "Model" which is used to interact with that table. Models allow you to query for data in your tables, as well as insert new records into the table. Before getting started, be sure to configure a database connection in config/database.php.
- 27. 27 Defining Models To get started, let's create an Eloquent model. Models typically live in the app directory, but you are free to place them anywhere. A l l E l o q u e n t m o d e l s e x t e n d IlluminateDatabaseEloquentModel class.
- 28. 28 Eloquent Model Conventions Now, let's look at an example Flight model, which we will use to retrieve and store information from our flights database table:
- 29. 29 Table Names Note that we did not tell Eloquent which table to use for our Flight model. By convention, the "snake case", plural name of the class will be used as the table name unless another name is explicitly specified. So, in this case, Eloquent will assume the Flight model stores records in the flights table. You may specify a custom table by defining a table property on your model:
- 30. 30 Primary Key Eloquent will also assume that each table has a primary key column named id. You may define a $primaryKey property to override this convention. In addition, Eloquent assumes that the primary key is an incrementing integer value, which means that by default the primary key will be cast to an int automatically. If you wish to use a non-incrementing or a non-numeric primary key you must set the public $incrementing property on your model to false.
- 31. 31 TimeStamps B y d e f a u l t , E l o q u e n t expects created_at and updated_at columns to exist on your tables. If you do not wish to have these columns automatically managed by Eloquent, set the $timestamps property on your model to false:
- 32. 32 TimeStamps
- 34. Retrieving Models 34 Once you have created a m o d e l a n d i t s associated database table, you are ready to start retrieving data from your database. Think of each Eloquent model as a powerful query builder allowing you to fluently query the database table associated with the model. For example:
- 35. 35 Chunk If you need to process thousands of Eloquent records, use the chunk command. The chunk method will retrieve a "chunk" of Eloquent models, feeding them to a given Closure for processing. Using the chunk method will conserve memory when working with large result sets:
- 36. 36 Cursor The cursor method allows you to iterate through your database records using a cursor, which will only execute a single query. When processing large amounts of data, the cursor method may be used to greatly reduce your memory usage:
- 37. 37 Retrieving Single Models / Aggregates
- 38. 38 Inserting & Updating Models
- 39. 39 Mass Updates
- 42. 42 UpdateOrCreate You may also come across situations where you want to update an existing model or create a new model if none exists. Laravel provides an updateOrCreate method to do this in one step. This Method persists the model, so there's no need to call save():