MySQL INSERT语句实现当记录不存在时插入的几种方法

INSERT IGNORE INTO table_name (column1, column2, ...)
VALUES (value1, value2, ...);

INSERT INTO table_name (column1, column2, ...)
VALUES (value1, value2, ...)
ON DUPLICATE KEY UPDATE column1 = VALUES(column1), column2 = VALUES(column2);

REPLACE INTO table_name (column1, column2, ...)
VALUES (value1, value2, ...);

INSERT INTO table_name (column1, column2, ...)
SELECT value1, value2, ...
FROM dual
WHERE NOT EXISTS (
    SELECT 1 FROM table_name 
    WHERE unique_column = unique_value
);

-- 方法1: INSERT IGNORE
INSERT IGNORE INTO users (username, email) VALUES ('john', 'john@example.com');

-- 方法2: ON DUPLICATE KEY UPDATE
INSERT INTO users (username, email) VALUES ('john', 'john@example.com')
ON DUPLICATE KEY UPDATE email = VALUES(email);

-- 方法3: REPLACE INTO
REPLACE INTO users (username, email) VALUES ('john', 'john@example.com');

-- 方法4: NOT EXISTS
INSERT INTO users (username, email)
SELECT 'john', 'john@example.com'
FROM dual
WHERE NOT EXISTS (
    SELECT 1 FROM users WHERE username = 'john'
);