mysql优先级队列

SELECT * FROM tasks ORDER BY priority DESC LIMIT 1;

-- 创建任务表
CREATE TABLE tasks (
    id INT AUTO_INCREMENT PRIMARY KEY,
    task TEXT,
    priority INT
);

-- 插入示例数据
INSERT INTO tasks (task, priority) VALUES ('Task A', 3);
INSERT INTO tasks (task, priority) VALUES ('Task B', 1);
INSERT INTO tasks (task, priority) VALUES ('Task C', 2);

-- 查询优先级最高的任务
SELECT * FROM tasks ORDER BY priority DESC LIMIT 1;

START TRANSACTION;
SELECT * FROM tasks WHERE id = (SELECT id FROM tasks ORDER BY priority DESC LIMIT 1) FOR UPDATE;
-- 处理任务
UPDATE tasks SET status = 'processed' WHERE id = (SELECT id FROM tasks ORDER BY priority DESC LIMIT 1);
COMMIT;

-- 创建任务表
CREATE TABLE tasks (
    id INT AUTO_INCREMENT PRIMARY KEY,
    task TEXT,
    priority INT,
    status VARCHAR(20)
);

-- 插入示例数据
INSERT INTO tasks (task, priority, status) VALUES ('Task A', 3, 'pending');
INSERT INTO tasks (task, priority, status) VALUES ('Task B', 1, 'pending');
INSERT INTO tasks (task, priority, status) VALUES ('Task C', 2, 'pending');

-- 处理优先级最高的任务
START TRANSACTION;
SELECT * FROM tasks WHERE id = (SELECT id FROM tasks ORDER BY priority DESC LIMIT 1) FOR UPDATE;
UPDATE tasks SET status = 'processed' WHERE id = (SELECT id FROM tasks ORDER BY priority DESC LIMIT 1);
COMMIT;

-- 设置事务隔离级别为READ COMMITTED
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;

START TRANSACTION;
SELECT * FROM tasks WHERE id = (SELECT id FROM tasks ORDER BY priority DESC LIMIT 1) FOR UPDATE;
-- 处理任务
UPDATE tasks SET status = 'processed' WHERE id = (SELECT id FROM tasks ORDER BY priority DESC LIMIT 1);
COMMIT;