例如有如下表结构：
CREATE TABLE `user_info` (`id` int(11) NOT NULL COMMENT 'id',`username` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '姓名',`idcard` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '身份证号',`nick_name` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '昵称',`remark` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '备注',PRIMARY KEY (`id`) USING BTREE,UNIQUE INDEX `idcard`(`idcard`) USING BTREE COMMENT '唯一身份标识') ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;
其中 id 是主键， idcard是唯一索引。