mysql - 查询中的许多项目的乘法计数

Question

这是我的查询:

SELECT
   `i`.`itemtype` AS `Item`,
   `p`.`name`
   SUM(`i`.`count`) AS `Count`
FROM `player_items` AS `i`
LEFT JOIN `players` AS `p` ON (`p`.`id` = `i`.`player_id`)
WHERE `i`.`itemtype` IN (2148, 2152, 2160)
   AND `i`.`player_id` = " . intval ( $main_Char->getId() ) . "
GROUP BY `i`.`itemtype`
LIMIT 0, 30;

是否有可能为它选择的每个项目增加一个计数？我的意思是 WHERE
i.itemtypeIN (2148, 2152, 2160)它对所有 ID 项目的计数求和:2148, 2152, 2160 我需要它来做同样的事情，但还要乘以每个项目的计数:2148 * 10， 2152 * 1000, 2160 * 10000 然后在 Count 行显示结果。

Answer 1

是的，您可以一次SUM多个列:

SELECT i.itemtype AS Item
   , p.name
   , SUM(CASE 
            WHEN itemtype = 2148 THEN i.count
            ELSE 0
         END) * 10 AS Count
   , SUM(CASE
            WHEN itemtype = 2152 THEN i.count
            ELSE 0
         END) * 1000 AS Count1
   , SUM(CASE
            WHEN itemtype = 2160 THEN i.count
            ELSE 0
         END) * 10000 AS Count2
FROM player_items AS i
LEFT JOIN players AS p ON i.player_id = p.id
WHERE i.itemtype IN (2148, 2152, 2160)
GROUP BY i.itemtype ASC
LIMIT 0, 30

要将这三列相加，您可以:

SELECT t.itemType AS Item, t.Count, t.Count1, t.Count2
   , SUM(t.Count1, t.Count2, t.Count3) AS Total
FROM
(
   SELECT i.itemtype AS Item
      , p.name
      , SUM(CASE 
               WHEN itemtype = 2148 THEN i.count
               ELSE 0
            END) * 10 AS Count
      , SUM(CASE
               WHEN itemtype = 2152 THEN i.count
               ELSE 0
            END) * 1000 AS Count1
      , SUM(CASE
               WHEN itemtype = 2160 THEN i.count
               ELSE 0
            END) * 10000 AS Count2
   FROM player_items AS i
   LEFT JOIN players AS p ON i.player_id = p.id
   WHERE i.itemtype IN (2148, 2152, 2160)
   GROUP BY i.itemtype ASC
   LIMIT 0, 30
) AS t

或者你可以添加另一个CASE

SELECT i.itemtype AS Item
   , p.name
   , SUM(CASE 
            WHEN itemtype = 2148 THEN i.count
            ELSE 0
         END) * 10 AS Count
   , SUM(CASE
            WHEN itemtype = 2152 THEN i.count
            ELSE 0
         END) * 1000 AS Count1
   , SUM(CASE
            WHEN itemtype = 2160 THEN i.count
            ELSE 0
         END) * 10000 AS Count2
   , SUM(CASE
            WHEN itemtype = 2148 THEN (i.count * 10)
            WHEN itemtype = 2152 THEN (i.count * 1000)
            WHEN itemtype = 2160 THEN (i.count * 10000)
            ELSE 0
         END) AS Total
FROM player_items AS i
LEFT JOIN players AS p ON i.player_id = p.id
WHERE i.itemtype IN (2148, 2152, 2160)
GROUP BY i.itemtype ASC
LIMIT 0, 30