mysql的插入更新操作 ON DUPLICATE KEY UPDATE

`SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

---

-- Table structure for user

---

DROP TABLE IF EXISTS user;
CREATE TABLE user (
uid int(11) NOT NULL AUTO_INCREMENT,
username varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL DEFAULT '',
password varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL DEFAULT '',
PRIMARY KEY (uid) USING BTREE,
UNIQUE INDEX username(username) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 5 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

---

-- Records of user

---

INSERT INTO user VALUES (1, 'admin', '123');
INSERT INTO user VALUES (2, '123', '456');

SET FOREIGN_KEY_CHECKS = 1;
`

唯一主键判断，若唯一主键重复执行修改，若不重复则插入，mysql方言

INSERT INTO USER ( username, password ) VALUES ( 'demo', '789' ) ON DUPLICATE KEY UPDATE username = 123, password = 456