Mysql stored procedure time month subtraction _ MySQL

Default2014-00-0000: 00: 00; declaretempTimeVARCHAR (19) defaultNOW (); declareendTimeVARCHAR (19) defaultDATE_SUB (tempTime, INTERVAL3MONTH declare startTime VARCHAR (19) default '2017-00-00 00:00:00 ';
Declare tempTime VARCHAR (19) default NOW ();
Declare endTime VARCHAR (19) default DATE_SUB (tempTime, INTERVAL '3' MONTH); -- three months after which

Declare monthstr varchar (7) default SUBSTR (endTime, 1, 7 );
Set endTime = CONCAT (MONTHSTR, '-00:00:00 ');


SELECT startTime as startTime, endTime AS endTime;