mysql - 查看帮助。从 3 个表中提取数据

Question

好的，我需要一些关于这个主题的重要帮助。这就是我需要 View 做的事情。需要取Attendance表中DKP_Change列的Sum

 SELECT SUM(a.DKP_Change) FROM Attendance AS a GROUP BY Name

从角色表中添加初始DKP的值

 SELECT b.Inital_DKP FROM Characters AS b GROUP BY Name

减去 raid drops tabe 成本的总和

 SELECT SUM(c.Cost) FROM Raid_Drops AS c GROUP BY Name

我对 VIEWS 的想法完全陌生，我不确定从哪里开始， View 的名称应该是 DKP，列应该是 Name 和 Total_DKP，其中总 dkp 是根据上面的选择计算的声明。

这是所有 3 个表的创建。

CREATE TABLE `Attendance` (
 `Date` date NOT NULL,
 `Name` varchar(20) NOT NULL,
 `Hours` int(11) NOT NULL,
 `Penalty` float NOT NULL,
 `Rank` set('Raider','Core','Elite') NOT NULL,
 `Rate` int(11) NOT NULL,
 `DKP_Change` float NOT NULL,
 `RecordNumber` int(11) NOT NULL AUTO_INCREMENT,
 PRIMARY KEY (`RecordNumber`)
) ENGINE=MyISAM AUTO_INCREMENT=15 DEFAULT CHARSET=latin1

CREATE TABLE `Characters` (
 `ID` int(11) NOT NULL AUTO_INCREMENT,
 `Name` varchar(25) NOT NULL,
 `Class` varchar(25) NOT NULL,
 `Spec` varchar(25) NOT NULL,
 `Position` set('Healer','Tank','DPS') NOT NULL COMMENT 'Healer, Tank, or DPS',
 `Usable` set('Cloth','Mail','Plate') NOT NULL COMMENT 'Type of Usable Armor? Cloth,        Mail, Or Plate',
 `Primary Stat` set('Agility','Strength','Intellect','Healer','Tank') NOT NULL COMMENT     'Used for Sorting Only(ie dps trinket with agility strength dps not eligible)',
 `Initial_DKP` int(11) NOT NULL COMMENT 'DKP given at the start of current tier.',
 `Total_DKP` int(11) NOT NULL COMMENT 'Huge Complicated Mess.',
 PRIMARY KEY (`ID`)
) ENGINE=MyISAM AUTO_INCREMENT=2 DEFAULT CHARSET=latin1

CREATE TABLE `Raid_Drops` (
 `Record Number` int(11) NOT NULL,
 `Date` date NOT NULL,
 `Name of Item` varchar(25) NOT NULL,
 `Item Slot` enum('Main Hand','Off Hand','Head','Neck','Shoulder','Back','Chest','Wrist','Hands','Waist','Legs','Feet','Ring 1','Ring 2','Trinket 1','Trinket 2') NOT NULL,
 `Player_Name` varchar(25) NOT NULL,
 `Cost` float NOT NULL,
 PRIMARY KEY (`Record Number`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1

Answer 1

你可以

• 在子选择中加入三个表，根据 Name 分组
• 对每个子选择的结果执行计算

我唯一不完全清楚的部分是 Characters 中的名称是否唯一。如果是，您可以删除该组。否则，AVG 可能会给您带来意想不到的结果。

SQL语句

SELECT sumA
       , initialB
       , sumC
       , sumA + initialB - sumC
       , a.Name
FROM   (
         SELECT Name, SUM(DKP_Change) AS sumA 
         FROM Attendance 
         GROUP BY Name
       ) AS a
       INNER JOIN (
         SELECT Name, Inital_DKP AS initialB 
         FROM Characters 
       ) AS b ON a.Name = b.Name
       INNER JOIN (
         SELECT Name, SUM(Cost) AS sumC 
         FROM Raid_Drops 
         GROUP BY Name
       ) AS c ON c.Name = b.Name