7.0 KiB
Database basics
Yii has a database access layer built on top of PHP's PDO. It provides uniform API and solves some inconsistencies between different DBMS. By default Yii supports the following DBMS:
Configuration
In order to start using database you need to configure database connection component first by adding db component
to application configuration (for "basic" web application it's config/web.php) like the following:
return [
// ...
'components' => [
// ...
'db' => [
'class' => 'yii\db\Connection',
'dsn' => 'mysql:host=localhost;dbname=mydatabase', // MySQL, MariaDB
//'dsn' => 'sqlite:/path/to/database/file', // SQLite
//'dsn' => 'pgsql:host=localhost;port=5432;dbname=mydatabase', // PostgreSQL
//'dsn' => 'cubrid:dbname=demodb;host=localhost;port=33000', // CUBRID
//'dsn' => 'sqlsrv:Server=localhost;Database=mydatabase', // MS SQL Server, sqlsrv driver
//'dsn' => 'dblib:host=localhost;dbname=mydatabase', // MS SQL Server, dblib driver
//'dsn' => 'mssql:host=localhost;dbname=mydatabase', // MS SQL Server, mssql driver
//'dsn' => 'oci:dbname=//localhost:1521/mydatabase', // Oracle
'username' => 'root',
'password' => '',
'charset' => 'utf8',
],
],
// ...
];
Please refer to the PHP manual for more details on the format of the DSN string.
After the connection component is configured you can access it using the following syntax:
$connection = \Yii::$app->db;
You can refer to \yii\db\Connection for a list of properties you can configure. Also note that you can define more than one connection component and use both at the same time if needed:
$primaryConnection = \Yii::$app->db;
$secondaryConnection = \Yii::$app->secondDb;
If you don't want to define the connection as an application component you can instantiate it directly:
$connection = new \yii\db\Connection([
'dsn' => $dsn,
'username' => $username,
'password' => $password,
]);
$connection->open();
Tip: if you need to execute additional SQL queries right after establishing a connection you can add the following to your application configuration file:
return [
// ...
'components' => [
// ...
'db' => [
'class' => 'yii\db\Connection',
// ...
'on afterOpen' => function($event) {
$event->sender->createCommand("SET time_zone = 'UTC'")->execute();
}
],
],
// ...
];
Basic SQL queries
Once you have a connection instance you can execute SQL queries using \yii\db\Command.
SELECT
When query returns a set of rows:
$command = $connection->createCommand('SELECT * FROM tbl_post');
$posts = $command->queryAll();
When only a single row is returned:
$command = $connection->createCommand('SELECT * FROM tbl_post WHERE id=1');
$post = $command->queryOne();
When there are multiple values from the same column:
$command = $connection->createCommand('SELECT title FROM tbl_post');
$titles = $command->queryColumn();
When there's a scalar value:
$command = $connection->createCommand('SELECT COUNT(*) FROM tbl_post');
$postCount = $command->queryScalar();
UPDATE, INSERT, DELETE etc.
If SQL executed doesn't return any data you can use command's execute method:
$command = $connection->createCommand('UPDATE tbl_post SET status=1 WHERE id=1');
$command->execute();
Alternatively the following syntax that takes care of proper table and column names quoting is possible:
// INSERT
$connection->createCommand()->insert('tbl_user', [
'name' => 'Sam',
'age' => 30,
])->execute();
// INSERT multiple rows at once
$connection->createCommand()->batchInsert('tbl_user', ['name', 'age'], [
['Tom', 30],
['Jane', 20],
['Linda', 25],
])->execute();
// UPDATE
$connection->createCommand()->update('tbl_user', ['status' => 1], 'age > 30')->execute();
// DELETE
$connection->createCommand()->delete('tbl_user', 'status = 0')->execute();
Quoting table and column names
Most of the time you would use the following syntax for quoting table and column names:
$sql = "SELECT COUNT([[$column]]) FROM {{$table}}";
$rowCount = $connection->createCommand($sql)->queryScalar();
In the code above [[X]] will be converted to properly quoted column name while {{Y}} will be converted to properly
quoted table name.
The alternative is to quote table and column names manually using \yii\db\Connection::quoteTableName() and \yii\db\Connection::quoteColumnName():
$column = $connection->quoteColumnName($column);
$table = $connection->quoteTableName($table);
$sql = "SELECT COUNT($column) FROM $table";
$rowCount = $connection->createCommand($sql)->queryScalar();
Prepared statements
In order to securely pass query parameters you can use prepared statements:
$command = $connection->createCommand('SELECT * FROM tbl_post WHERE id=:id');
$command->bindValue(':id', $_GET['id']);
$post = $command->query();
Another usage is performing a query multiple times while preparing it only once:
$command = $connection->createCommand('DELETE FROM tbl_post WHERE id=:id');
$command->bindParam(':id', $id);
$id = 1;
$command->execute();
$id = 2;
$command->execute();
Transactions
If the underlying DBMS supports transactions, you can perform transactional SQL queries like the following:
$transaction = $connection->beginTransaction();
try {
$connection->createCommand($sql1)->execute();
$connection->createCommand($sql2)->execute();
// ... executing other SQL statements ...
$transaction->commit();
} catch(Exception $e) {
$transaction->rollback();
}
Working with database schema
Getting schema information
You can get a \yii\db\Schema instance like the following:
$schema = $connection->getSchema();
It contains a set of methods allowing you to retrieve various information about the database:
$tables = $schema->getTableNames();
For the full reference check \yii\db\Schema.
Modifying schema
Aside from basic SQL queries \yii\db\Command contains a set of methods allowing to modify database schema:
- createTable, renameTable, dropTable, truncateTable
- addColumn, renameColumn, dropColumn, alterColumn
- addPrimaryKey, dropPrimaryKey
- addForeignKey, dropForeignKey
- createIndex, dropIndex
These can be used as follows:
// CREATE TABLE
$connection->createCommand()->createTable('tbl_post', [
'id' => 'pk',
'title' => 'string',
'text' => 'text',
];
For the full reference check \yii\db\Command.