Need help writing the case statement - MySQL Cursor - mysql

Question

I created two columns in student table for my database. I now need to create a cursor for the student table. I need to make use of the input parameters for start and end student Id’s to filter the results in the cursor query.
I also need to open the cursor created and check if the student has an email assigned or not. If the email is not assigned I need to update the email column to have an email assigned to the student.
Finally to why I want help:
I cannot figure out how I would write the case statements for this cursor. I have tried to think of a good way to do this and not succeeded. Please help!!
DELIMITER $
DROP PROCEDURE IF EXISTS CURSOR_DEMO$
CREATE PROCEDURE CURSOR_DEMO(start_student_id INT
,end_student_id INT
)
BEGIN
DECLARE l_table_name VARCHAR(50);
DECLARE iam_done INT DEFAULT 0;
DECLARE l_sql_stmt VARCHAR(5000);
SET #l_sql_stmt='ALTER TABLE STUDENT ADD EMAIL VARCHAR';
SELECT #l_sql_stmt;
prepare stmt from #l_sql_stmt;
execute stmt;
SET #l_sql_stmt='ALTER TABLE STUDENT ADD PHONE int(10)';
SELECT #l_sql_stmt;
prepare stmt from #l_sql_stmt;
execute stmt;
DECLARE TBL_CUR CURSOR FOR
SELECT EMAIL FROM STUDENT.TABLES WHERE TABLE_SCHEMA='MYSQLDB';
BEGIN
DECLARE CONTINUE HANDLER FOR NOT FOUND SET IAM_DONE=1;
OPEN TBL_CUR;
tbl_loop:LOOP
FETCH tbl_cur INTO l_table_name;
IF IAM_DONE = 1 THEN
LEAVE tbl_loop;
END IF;
CASE WHEN l_table_name = 'STUDENT' THEN
ELSE BEGIN END;
END CASE;
END LOOP tbl_loop;
CLOSE TBL_CUR;
END;
END$
DELIMITER ;

Answer 1

Is this the kind of thing you need?
/*
drop table student;
delimiter $$
CREATE TABLE `student` (
`id` int(11) NOT NULL ,
`name` char(1) NOT NULL,
`email` varchar(1),
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8$$
drop table email;
delimiter $$
CREATE TABLE `email` (
`id` int(11) NOT NULL ,
`type` varchar(8) NOT NULL,
`person_id` int,
`email` varchar(1),
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8$$
;
*/
DELIMITER $
DROP PROCEDURE IF EXISTS CURSOR_DEMO$
CREATE PROCEDURE CURSOR_DEMO(start_student_id INT
,end_student_id INT)
BEGIN
declare email_person_id int;
declare email_address varchar(50);
DECLARE done INT DEFAULT 0;
DECLARE CUR CURSOR FOR
SELECT person_id,email FROM sandbox.email where type = 'student';
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;
OPEN CUR;
cur_loop:LOOP
IF done = 1 THEN
LEAVE cur_loop;
END IF;
FETCH CUR INTO email_person_id,email_address;
update student
set email = email_address
where id = email_person_id
and email is null
;
END LOOP cur_loop;
CLOSE CUR;
commit;
END$
DELIMITER ;
truncate table student;
insert into student
values
(1,'A','1'),
(2,'B','1'),
(3,'C',null),
(4,'D',null),
(5,'E',null),
(6,'G',null),
(7,'F',null)
;
truncate table email;
insert into email
values
(1,'student',1,'a'),
(2,'student',2,'b'),
(3,'faculty',7,'z'),
(4,'student',3,'c')
;
select * from student;
call cursor_demo(1,10);
select * from student;