added docs about DB table and column quoting

docs/guide/database-basics.md

@@ -105,7 +105,7 @@ $command = $connection->createCommand('UPDATE tbl_post SET status=1 WHERE id=1')
 $command->execute();
 ```
 
-Alternatively the following syntax is possible:
+Alternatively the following syntax that takes care of proper table and column names quoting is possible:
 
 ```php
 // INSERT
@@ -130,6 +130,29 @@ $connection->createCommand()->update('tbl_user', array(
 $connection->createCommand()->delete('tbl_user', 'status = 0')->execute();
 ```
 
+Quoting table and column names
+------------------------------
+
+If you are building query string dynamically make sure you're properly quoting table and column names using
+[[\yii\db\Connection::quoteTableName()]] and [[\yii\db\Connection::quoteColumnName()]]:
+
+```php
+$column = $connection->quoteColumnName($column);
+$table = $connection->quoteTableName($table);
+$sql = "SELECT COUNT($column) FROM $table";
+$rowCount = $connection->createCommand($sql)->queryScalar();
+```
+
+Alternatively you can use special syntax when writing SQL:
+
+```php
+$sql = "SELECT COUNT({{$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.
+
 
 Prepared statements
 -------------------