参考：https://github.com/yii2-chinesization/yii2-zh-cn/blob/master/guide-zh-cn/db-dao.md
返回多行：
$command = $connection->createcommand('select * from post');$posts = $command->queryall();
翻译单行：
$command = $connection->createcommand('select * from post where id=1');$post = $command->queryone();
查询多列：
$command = $connection->createcommand('select title from post');$titles = $command->querycolumn();
查询标量/计算值：
$command = $connection->createcommand('select count(*) from post');$postcount = $command->queryscalar();
更新数据：
$command = $connection->createcommand('update post set status=1 where id=1');$command->execute();
一次插入单行/多行：
// insert $connection->createcommand()->insert('user', [ 'name' => 'sam', 'age' => 30, ])->execute();// insert 一次插入多行 $connection->createcommand()->batchinsert('user', ['name', 'age'], [ ['tom', 30], ['jane', 20], ['linda', 25], ])->execute();
更新：
$connection->createcommand()->update('user', ['status' => 1], 'age > 30')->execute();
删除：
$connection->createcommand()->delete('user', 'status = 0')->execute();
预处理：
$command = $connection->createcommand('select * from post where id=:id');$command->bindvalue(':id', $_get['id']);$post = $command->query();
一次预处理语句执行多次：
$command = $connection->createcommand('delete from post where id=:id');$command->bindparam(':id', $id); $id = 1;$command->execute(); $id = 2;$command->execute();
建表：
$connection->createcommand()->createtable('post', [ 'id' => 'pk', 'title' => 'string', 'text' => 'text',]);