The source of the MYSQL case, thanks to the case provided by netizens, based on it, simplified, although it does not meet the database paradigm, but it is enough to explain the problem
The original requirements are as follows:
The known source table data is as follows:
| PID | on one | Place | |||
| Apple | 11 | Beijing warehouse | |||
| banana | 22 | Shanghai warehouse | |||
| big pear | 44 | Guangzhou warehouse | |||
| Apple | 66 | Shenzhen warehouse |
Now it is required to get the inventory report of each commodity, which is convenient for unified scheduling and display
| PID | Beijing warehouse | Shanghai warehouse | Guangzhou warehouse | Shenzhen warehouse | …… |
| Apple | 11 | 0 | 0 | 66 | |
| banana | 0 | 22 | 0 | 0 | |
| big pear | 0 | 0 | 44 | 0 |
Solution one:
Solution two:
Solution three:
Appendix:
/*
Navicat MySQL Data Transfer
Source Server : localhost
Source Server Version : 50547
Source Host : localhost:3306
Source Database : db1
Target Server Type : MYSQL
Target Server Version : 50547
File Encoding : 65001
Date: 2017-07-09 17:58:13
*/
SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for `p`
-- ----------------------------
DROP TABLE IF EXISTS `p`;
CREATE TABLE `p` (
`id` int(11) NOT NULL DEFAULT '0',
`pid` varchar(30) DEFAULT NULL,
`num` int(11) DEFAULT NULL,
`loc` varchar(30) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of p
-- ----------------------------
INSERT INTO `p` VALUES ('1', 'Apple', '11', 'Beijing warehouse');
INSERT INTO `p` VALUES ('2', 'banana', '22', 'Shanghai warehouse');
INSERT INTO `p` VALUES ('3', 'Da Yali', '44', 'Guangzhou warehouse');
INSERT INTO `p` VALUES ('4', 'Apple', '66', 'Shenzhen warehouse');