mysql - MySQL查询中的查询语法错误

Question

这是我的查询:

SELECT
   `i`.`itemtype` AS `Item`,
   `p`.`name`
   (SELECT SUM(`i`.`count`) AS `Count` WHERE `itemtype` = 2148),
   (SELECT SUM(`i`.`count`) * 100 AS `Count1` WHERE `itemtype` = 2152),
   (SELECT SUM(`i`.`count`) * 10000 AS `Count2` WHERE `itemtype` = 2160)
FROM `player_items` AS `i`
LEFT JOIN `players` AS `p` ON (`p`.`id` = `i`.`player_id`)
WHERE `i`.`itemtype` IN (2148, 2152, 2160)
GROUP BY `i`.`itemtype`
LIMIT 0, 30

当我在 mysql 中运行上面的查询时，我得到这个错误信息:

#1064 - You have an error in your SQL syntax; check the manual that corresponds
to your MySQL server version for the right syntax to use near
'SELECT SUM(`i`.`count`) AS `Count` WHERE `itemtype` = 2148)
   , (SELECT SUM(`i`' at line 4

我完全不明白这是什么意思，因为我是 MySQL 的初学者。

Answer 1

此列后缺少逗号:

`p`.`name`

改为考虑这个查询:

SELECT i.itemtype AS Item
   , p.name
   , SUM(CASE 
            WHEN itemtype = 2148 THEN i.count
            ELSE 0
         END) AS Count
   , SUM(CASE
            WHEN itemtype = 2152 THEN i.count
            ELSE 0
         END) * 100 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) AS Count
      , SUM(CASE
               WHEN itemtype = 2152 THEN i.count
               ELSE 0
            END) * 100 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) AS Count
   , SUM(CASE
            WHEN itemtype = 2152 THEN i.count
            ELSE 0
         END) * 100 AS Count1
   , SUM(CASE
            WHEN itemtype = 2160 THEN i.count
            ELSE 0
         END) * 10000 AS Count2
   , SUM(CASE
            WHEN itemtype = 2148 THEN i.count
            WHEN itemtype = 2152 THEN (i.count * 100)
            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

CASE statements使您不必运行三个额外的 SELECT 语句来返回相同的结果。