How to declare a cursor in mysql

How to declare a cursor in mysql:

1. Declare variables and cursors

declare result varchar(3000);
declare flag1 varchar(100);
DECLARE done INT DEFAULT FALSE;
declare cur1 CURSOR FOR SELECT flag from bmlx;

2. Variable assignment

DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
set result = '';

3. Open cursor and loop

open cur1;
read_loop: LOOP

-- Assign a value to the cursor

FETCH cur1 INTO flag1;

-- Break out of the loop

IF done THEN
LEAVE read_loop;
END IF;

-- Loop to get cursor data and accumulate

set result = CONCAT(result, flag1 ,',');
END LOOP;

-- Close the cursor

close cur1;

-- Return parameter

set result = CONCAT(result,'<span style="color:Red">');
RETURN result;

Content extension:

The entire process of using the MySQL cursor is:

1. Create a cursor

DECLARE calc_bonus CURSOR FOR SELECT id, salary, commission FROM employees;

2. Open the cursor

OPEN calc_bonus;

3. Use cursor

FETCH calc_bonus INTO re_id, re_salary, re_comm;

4. Close the cursor

CLOSE calc_bonus;

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