Cursors in MySQL

What is a Cursor?

Cursor Structure

DECLARE done INT DEFAULT 0;
DECLARE v_name VARCHAR(50);
DECLARE cur CURSOR FOR SELECT name FROM students;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

OPEN cur;
read_loop: LOOP
    FETCH cur INTO v_name;
    IF done = 1 THEN LEAVE read_loop; END IF;
    -- process v_name here
END LOOP;
CLOSE cur;

When to Use

Summary

• A cursor processes rows one by one inside a procedure.
• Steps: DECLARE, OPEN, FETCH in a loop, CLOSE. Use sparingly.

Cursor क्या है?

Cursor Structure

DECLARE done INT DEFAULT 0;
DECLARE v_name VARCHAR(50);
DECLARE cur CURSOR FOR SELECT name FROM students;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

OPEN cur;
read_loop: LOOP
    FETCH cur INTO v_name;
    IF done = 1 THEN LEAVE read_loop; END IF;
    -- यहाँ v_name process करें
END LOOP;
CLOSE cur;

कब Use करें

सारांश

• Cursor procedure के अंदर rows एक-एक करके process करता है।
• Steps: DECLARE, OPEN, loop में FETCH, CLOSE। कम use करें।