mysql联合主键插入时

-- 创建表时定义联合主键
CREATE TABLE example (
    id INT,
    name VARCHAR(50),
    age INT,
    PRIMARY KEY (id, name)
);

-- 插入数据前检查是否存在
INSERT INTO example (id, name, age)
SELECT * FROM (SELECT 1 AS id, 'Alice' AS name, 25 AS age) AS tmp
WHERE NOT EXISTS (
    SELECT id, name FROM example WHERE id = 1 AND name = 'Alice'
);

-- 使用INSERT IGNORE忽略重复数据
INSERT IGNORE INTO example (id, name, age) VALUES (1, 'Alice', 25);

-- 或者使用ON DUPLICATE KEY UPDATE处理重复数据
INSERT INTO example (id, name, age) VALUES (1, 'Alice', 25)
ON DUPLICATE KEY UPDATE age = 26;

-- 确保插入的数据中联合主键的所有字段都不为空
INSERT INTO example (id, name, age) VALUES (1, 'Alice', 25);