Question

您好我试图将这样的多个总和加起来：

$_.PSIsContainer

但SELECT `users`.*, @attackPower := FLOOR(SUM(IF( `weapons`.`weaponeType` = 'atk',`weapons`.`weaponPower` * `weapons_has_users`.`count` , 0 ) )) AS `attackPower` , @defencePower := FLOOR(SUM(IF( `weapons`.`weaponeType` = 'def', `weapons`.`weaponPower` * `weapons_has_users`.`count` , 0 ) )) AS `defencePower`, @spyPower := FLOOR(SUM(IF( `weapons`.`weaponeType` = 'spy', `weapons`.`weaponPower` * `weapons_has_users`.`count` , 0 ) )) AS `spyPower`, @uniPower := FLOOR(SUM(IF( `weapons`.`weaponeType` = 'uni', `weapons`.`weaponPower` * `weapons_has_users`.`count` , 0 ) )) AS `uniPower`, (@attackPower + @defencePower + @spyPower + @uniPower) as `power` FROM `users` LEFT JOIN `weapons_has_users` ON `users`.`userId` = `weapons_has_users`.`userId` LEFT JOIN `weapons` ON `weapons`.`weaponId` = `weapons_has_users`.`weaponId`返回NULL 我能做些什么来解决这个问题？

Answer 1

MySQL文档专门警告不要在同一语句中分配和使用变量。

此外，如果要在查询中使用聚合函数（并且希望返回多行），则需要子查询。

因为您需要使用聚合，所以您也可以使用子查询：

select u.*,
    (attackPower + defencePower + spyPower + uniPower) as `power`
from (SELECT `users`.*,
             FLOOR(SUM(IF( `weapons`.`weaponeType` = 'atk',`weapons`.`weaponPower` * `weapons_has_users`.`count` , 0 ) )) AS `attackPower` ,
             FLOOR(SUM(IF( `weapons`.`weaponeType` = 'def', `weapons`.`weaponPower` * `weapons_has_users`.`count` , 0 ) )) AS `defencePower`,
             FLOOR(SUM(IF( `weapons`.`weaponeType` = 'spy', `weapons`.`weaponPower` * `weapons_has_users`.`count` , 0 ) )) AS `spyPower`,
             FLOOR(SUM(IF( `weapons`.`weaponeType` = 'uni', `weapons`.`weaponPower` * `weapons_has_users`.`count` , 0 ) )) AS `uniPower`,

      FROM `users` LEFT JOIN
           `weapons_has_users`
           ON `users`.`userId` = `weapons_has_users`.`userId` LEFT JOIN
           `weapons`
           ON `weapons`.`weaponId` = `weapons_has_users`.`weaponId`
      GROUP BY users.id
    ) u;

在mysql中尝试多次求和

1 个答案: