MySQL中的DELETE删除数据及注意事项

DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM table_name
[WHERE condition]
[ORDER BY ...]
[LIMIT row_count]

-- 删除表 students 中 id 为 1 的记录
DELETE FROM students
WHERE id = 1;
-- 删除表 students 中所有记录
DELETE FROM students;

-- 删除表 students 中 class_id 为表 classes 中 name 为 '数学班' 的 class_id 的记录
DELETE FROM students
WHERE class_id = (SELECT id FROM classes WHERE name = '数学班');

-- 删除表 orders 和 order_details 中订单总金额大于 1000 的记录
DELETE o, od
FROM orders o
JOIN order_details od ON o.order_id = od.order_id
WHERE o.total_amount > 1000;

-- 删除表 students 中按年龄降序排列的前 3 名学生
DELETE FROM students
ORDER BY age DESC
LIMIT 3;

-- 删除表 students 中重复的 email 记录，保留 id 更小的一条记录
DELETE e1
FROM students e1, students e2
WHERE e1.id > e2.id AND e1.email = e2.email;

-- 假设 id 字段有索引
DELETE FROM students
WHERE id = 1;

-- 批量删除多个记录
DELETE FROM employees
WHERE id IN (1, 2, 3);

-- 避免这种写法
DELETE FROM employees;

-- 清空表 students
TRUNCATE TABLE students;

START TRANSACTION;
DELETE FROM employees
WHERE id BETWEEN 1 AND 1000;
COMMIT;
START TRANSACTION;
DELETE FROM employees
WHERE id BETWEEN 1001 AND 2000;
COMMIT;

-- 删除 id 为 1 的员工的记录
DELETE FROM employees
WHERE id = 1;

-- 删除部门为 10 的所有员工的记录
DELETE FROM employees
WHERE department_id = 10;

-- 删除表 employees 中重复的 email 记录，保留 id 更小的一条记录
DELETE e1
FROM employees e1, employees e2
WHERE e1.id > e2.id AND e1.email = e2.email;

-- 删除表 employees 中 department_id 为表 departments 中 name 为 '研发部' 的 department_id 的记录
DELETE FROM employees
WHERE department_id = (SELECT id FROM departments WHERE name = '研发部');

-- 删除表 employees 中按工资降序排列的前 3 名员工
DELETE FROM employees
ORDER BY salary DESC
LIMIT 3;