实现mysql存储过程双层循环遍历

流程表格

步骤 操作
1 创建存储过程
2 声明游标
3 打开游标
4 循环外层游标
5 声明内层游标
6 打开内层游标
7 循环内层游标
8 关闭内层游标
9 循环外层游标
10 关闭外层游标

操作步骤及代码

步骤1：创建存储过程

CREATE PROCEDURE doubleLoop()
BEGIN
    -- 存储过程内容在这里编写
END

步骤2：声明游标

DECLARE outer_cursor CURSOR FOR
SELECT outer_column FROM outer_table;
DECLARE inner_cursor CURSOR FOR
SELECT inner_column FROM inner_table;

步骤3：打开游标

OPEN outer_cursor;
OPEN inner_cursor;

步骤4：循环外层游标

outer_loop: LOOP
    FETCH outer_cursor INTO outer_variable;
    IF done THEN
        LEAVE outer_loop;
    END IF;

步骤5：声明内层游标

DECLARE inner_cursor CURSOR FOR
SELECT inner_column FROM inner_table;

步骤6：打开内层游标

OPEN inner_cursor;

步骤7：循环内层游标

inner_loop: LOOP
    FETCH inner_cursor INTO inner_variable;
    IF done THEN
        LEAVE inner_loop;
    END IF;

步骤8：关闭内层游标

CLOSE inner_cursor;

步骤9：循环外层游标

END LOOP inner_loop;
END LOOP outer_loop;

步骤10：关闭外层游标

CLOSE outer_cursor;

类图

classDiagram
    class Developer {
        - name: string
        - experience: int
        + teachBeginner(): void
    }
    class Beginner {
        - name: string
        - experience: int
        + learn(): void
    }
    Developer <-- Beginner

状态图

stateDiagram
    [*] --> Beginner
    Beginner --> Learning: learn()
    Learning --> Implementing: practice()
    Implementing --> [*]

通过以上步骤和代码，你应该能够实现mysql存储过程双层循环遍历了。希望这篇文章能够帮助到你，祝你学习顺利！