reverted #1598 and added a test for it

framework/yii/db/Query.php

@@ -148,7 +148,7 @@ class Query extends Component implements QueryInterface
 	 * Executes the query and returns a single row of result.
 	 * @param Connection $db the database connection used to generate the SQL statement.
 	 * If this parameter is not given, the `db` application component will be used.
-	 * @return array|boolean the first row (in terms of an array) of the query result. Null is returned if the query
+	 * @return array|boolean the first row (in terms of an array) of the query result. False is returned if the query
 	 * results in nothing.
 	 */
 	public function one($db = null)

tests/unit/framework/db/QueryTest.php

@@ -112,4 +112,15 @@ class QueryTest extends DatabaseTestCase
 	public function testUnion()
 	{
 	}
+
+	public function testOne()
+	{
+		$db = $this->getConnection();
+
+		$result = (new Query)->from('tbl_customer')->where(['status' => 2])->one($db);
+		$this->assertEquals('user3', $result['name']);
+
+		$result = (new Query)->from('tbl_customer')->where(['status' => 3])->one($db);
+		$this->assertFalse($result);
+	}
 }