Невозможно импортировать функцию MYSQL - ОШИБКА 1064 (42000)

Я пытаюсь понять, почему следующее не работает, и я не могу его увидеть. PhpMyAdmin на нашем сервере разработки сгенерировал это точно, но когда я попытаюсь импортировать его - я столкнулся с странной ошибкой синтаксического анализа (?).

mysql> DELIMITER $$
mysql>
mysql> --
mysql> -- Functions
mysql> --
mysql> DROP FUNCTION IF EXISTS `get_class_nextsession`$$
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> CREATE DEFINER=`myusername`@`localhost` FUNCTION `get_class_nextsession`(class_id INT) RETURNS datetime
    ->     READS SQL DATA
    -> BEGIN
    -> DECLARE nextsession,startdate,runningdate,enddate DATETIME;
    -> SET nextsession= '-';
    -> SELECT  MIN(CS.start_datetime) INTO startdate FROM site_class_schedule AS CS INNER JOIN site_class AS C ON (C.id=CS.class_id) WHERE CS.class_id=class_id Group by C.id Limit 0,1;
    -> IF startdate >= NOW() THEN
    -> RETURN startdate;
    -> ELSE
    -> SELECT  CS.start_datetime INTO runningdate FROM site_class_schedule AS CS INNER JOIN site_class AS C ON (C.id=CS.class_id) WHERE CS.class_id=class_id and (NOW() between start_datetime and end_datetime ) Limit 0,1;
    -> IF runningdate IS NOT NULL THEN
    -> RETURN runningdate;
    -> ELSE
    -> SELECT  MAX(CS.end_datetime) INTO enddate FROM site_class_schedule AS CS INNER JOIN site_class AS C ON (C.id=CS.class_id) WHERE CS.class_id=class_id Group by C.id Limit 0,1;
    -> IF enddate < NOW() THEN
    -> RETURN enddate;
    -> ELSEIF enddate >= NOW() THEN
    -> SELECT  MIN(CS.start_datetime) INTO startdate FROM site_class_schedule AS CS INNER JOIN site_class AS C ON (C.id=CS.class_id) WHERE CS.class_id=class_id and CS.start_datetime > NOW() Group by C.id Limit 0,1;
    ->
Display all 1866 possibilities? (y or n)
    ->  startdate;
    ->
Display all 1866 possibilities? (y or n)
    -> D IF;
    -> END IF;
    -> END IF;
    -> RETURN nextsession;
    -> END$$
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ';
D IF;
END IF;
END IF;
RETURN nextsession;
END' at line 19
mysql>
mysql>

Обновление выполнения 1

Это РАБОТАЕТ

mysql> DELIMITER $$
mysql>
mysql> DROP FUNCTION IF EXISTS `get_class_nextsession`$$
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> CREATE DEFINER=`myusername`@`localhost` FUNCTION `get_class_nextsession`(class_id INT) RETURNS datetime
    ->     READS SQL DATA
    -> BEGIN
    -> RETURN nextsession;
    -> END$$
Query OK, 0 rows affected (0.00 sec)

Это РАБОТАЕТ

mysql>
mysql> DROP FUNCTION IF EXISTS `get_class_nextsession`$$
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> CREATE DEFINER=`myusername`@`localhost` FUNCTION `get_class_nextsession`(class_id INT) RETURNS datetime
    ->     READS SQL DATA
    -> BEGIN
    -> DECLARE nextsession,startdate,runningdate,enddate DATETIME;
    -> RETURN nextsession;
    -> END$$
Query OK, 0 rows affected (0.00 sec)

Это НЕ РАБОТАЕТ - Обратите внимание, как я пытаюсь упростить запрос/заявления в базовые.

mysql> DROP FUNCTION IF EXISTS `get_class_nextsession`$$
Query OK, 0 rows affected, 1 warning (0.01 sec)

mysql> CREATE DEFINER=`myusername`@`localhost` FUNCTION `get_class_nextsession`(class_id INT) RETURNS datetime
    ->     READS SQL DATA
    -> BEGIN
    -> DECLARE nextsession,startdate,runningdate,enddate DATETIME;
    -> SET nextsession= '-';
    -> SELECT  MIN(start_datetime) INTO startdate FROM site_class_schedule;
    -> IF startdate >= NOW() THEN
    -> RETURN startdate;
    -> ELSE
    -> END IF;
    -> RETURN nextsession;
    -> END$$
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'END IF;
RETURN nextsession;
END' at line 10