环比求助

DROP TABLE IF EXISTS `itest`;

CREATE TABLE `itest`  (

  `date` date NOT NULL,

  `num` int(11) DEFAULT NULL,

  PRIMARY KEY (`date`) USING BTREE

) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;



-- ----------------------------

-- Records of itest

-- ----------------------------

INSERT INTO `itest` VALUES ('2018-02-01', 100);

INSERT INTO `itest` VALUES ('2018-02-02', 0);

INSERT INTO `itest` VALUES ('2018-02-03', 0);

INSERT INTO `itest` VALUES ('2018-02-04', 90);

INSERT INTO `itest` VALUES ('2018-02-05', 95);

INSERT INTO `itest` VALUES ('2018-02-06', 0);

INSERT INTO `itest` VALUES ('2018-02-07', 80);