MySQL内部连接where子句排序和限制，子查询？

以下查询中的所有内容将为每个invBlueprintTypes行生成一行，其中包含正确的信息。但我想给它添加点东西。请参见下面的代码块

Select
  blueprintType.typeID,
  blueprintType.typeName Blueprint,
  productType.typeID,
  productType.typeName Item,
  productType.portionSize,
  blueprintType.basePrice * 0.9 As bpoPrice,
  productGroup.groupName ItemGroup,
  productCategory.categoryName ItemCategory,
  blueprints.productionTime,
  blueprints.techLevel,
  blueprints.researchProductivityTime,
  blueprints.researchMaterialTime,
  blueprints.researchCopyTime,
  blueprints.researchTechTime,
  blueprints.productivityModifier,
  blueprints.materialModifier,
  blueprints.wasteFactor,
  blueprints.maxProductionLimit,
  blueprints.blueprintTypeID
From
  invBlueprintTypes As blueprints
  Inner Join invTypes As blueprintType On blueprints.blueprintTypeID = blueprintType.typeID
  Inner Join invTypes As productType On blueprints.productTypeID = productType.typeID
  Inner Join invGroups As productGroup On productType.groupID = productGroup.groupID
  Inner Join invCategories As productCategory On productGroup.categoryID = productCategory.categoryID
Where
  blueprints.techLevel = 1 And
  blueprintType.published = 1 And
  productType.marketGroupID Is Not Null And
  blueprintType.basePrice > 0

因此，我需要在这里得到的是下表及其下的列，这样我就可以使用值timestamp并按profitHour对整个结果进行排序

tablename: invBlueprintTypesPrices
columns:   blueprintTypeID, timestamp, profitHour

我需要这些信息，并牢记以下选择。使用select来显示我的JOIN/in查询意图select或任何可以执行此操作的工具

SELECT * FROM invBlueprintTypesPrices 
WHERE blueprintTypeID = blueprintType.typeID 
ORDER BY timestamp DESC LIMIT 1

我需要表invBlueprintTypes中的主行仍然显示，即使invBlueprintTypesPrices没有结果。限制1是因为我希望尽可能使用最新的行，但由于需要历史记录，因此不能删除较旧的数据

如果我理解正确的话，我想我需要一个子查询select，但是怎么做呢？我已经厌倦了在查询结束后添加上面带有AS blueprintPrices的确切查询，但是没有在

WHERE blueprintTypeID = blueprintType.typeID

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部分是错误的焦点。我不知道为什么。有人能解决这个问题吗？

你不能说你把子查询放在哪里。如果在select子句中，则会出现问题，因为返回的值不止一个

不能直接将其放入from子句中，因为不允许使用相关子查询

相反，您可以这样将其放入：

from . . .
     (select *
      from invBLueprintTypesPrices ibptp
      where ibtp.timestamp = (select ibptp2.timestamp
                              from invBLueprintTypesPrices ibptp2
                              where ibptp.blueprintTypeId = ibptp2.blueprintTypeId
                              order by timestamp desc
                              limit 1
                             )
     ) ibptp
     on ibptp.blueprintTypeId = blueprintType.TypeID

这将标识子查询中所有BlueprintTypeID的最新记录。然后它加入匹配的一个。

您需要使用左连接来检查invBlueprintTypesPrices中的空值。要模拟每个类型id的限制1，您可以使用MAX，或者为了真正确保只返回一条记录，请使用行号-这取决于您是否可以为每个类型id设置多个MAX时间戳。如果没有，则应关闭：

Select
  ...
From
  invBlueprintTypes As blueprints
  Inner Join invTypes As blueprintType On blueprints.blueprintTypeID = blueprintType.typeID
  Inner Join invTypes As productType On blueprints.productTypeID = productType.typeID
  Inner Join invGroups As productGroup On productType.groupID = productGroup.groupID
  Inner Join invCategories As productCategory On productGroup.categoryID = productCategory.categoryID
  Left Join (
    SELECT MAX(TimeStamp) MaxTime, TypeId
    FROM invBlueprintTypesPrices 
    GROUP BY TypeId
  ) blueprintTypePrice On blueprints.blueprintTypeID = blueprintTypePrice.typeID 
  Left Join invBlueprintTypesPrices blueprintTypePrices On 
    blueprintTypePrice.TypeId = blueprintTypePrices.TypeId AND
    blueprintTypePrice.MaxTime = blueprintTypePrices.TimeStamp 
Where
  blueprints.techLevel = 1 And
  blueprintType.published = 1 And
  productType.marketGroupID Is Not Null And
  blueprintType.basePrice > 0
Order By
  blueprintTypePrices.profitHour

假设您可能有相同的最大时间戳和两个不同的记录，将上面的两个左连接替换为类似的内容，获取行号：

Left Join (
    SELECT @rn:=IF(@prevTypeId=TypeId,@rn+1,1) rn, 
         TimeStamp, 
         TypeId, 
         profitHour, 
         @prevTypeId:=TypeId
    FROM (SELECT * 
          FROM invBlueprintTypesPrices 
          ORDER BY TypeId, TimeStamp DESC) t
       JOIN (SELECT @rn:=0) t2
  ) blueprintTypePrices On blueprints.blueprintTypeID = blueprintTypePrices.typeID AND blueprintTypePrices.rn=1

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我没有提到我把子查询放在哪里，因为我尝试了几个地方，但都不起作用，我知道它应该放在哪里。但我想我现在知道了。无法让您的回复完全按照我的要求工作，但很接近。通过斯格迪斯的回答解决了这个问题。谢谢你