MySql在数据库中迭代

DELIMITER //

CREATE PROCEDURE IterateThroughTable()
BEGIN
  DECLARE done INT DEFAULT FALSE;
  DECLARE id INT;
  DECLARE cur CURSOR FOR SELECT id FROM your_table;
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

  OPEN cur;

  read_loop: LOOP
    FETCH cur INTO id;
    IF done THEN
      LEAVE read_loop;
    END IF;
    -- 在这里执行对每条记录的操作，例如打印ID
    SELECT id;
  END LOOP;

  CLOSE cur;
END //

DELIMITER ;

DELIMITER //

CREATE PROCEDURE UseCursorToIterate()
BEGIN
  DECLARE done INT DEFAULT FALSE;
  DECLARE id INT;
  DECLARE cur CURSOR FOR SELECT id FROM your_table;
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

  OPEN cur;

  read_loop: LOOP
    FETCH cur INTO id;
    IF done THEN
      LEAVE read_loop;
    END IF;
    -- 在这里执行对每条记录的操作
    -- ...
  END LOOP;

  CLOSE cur;
END //

DELIMITER ;

DELIMITER //

CREATE PROCEDURE LoopThroughTable()
BEGIN
  DECLARE i INT DEFAULT 0;
  DECLARE total INT DEFAULT (SELECT COUNT(*) FROM your_table);

  WHILE i < total DO
    -- 在这里执行对每条记录的操作，例如获取第i条记录
    SELECT * FROM your_table LIMIT i, 1;
    SET i = i + 1;
  END WHILE;
END //

DELIMITER ;