返回特定列的情況

Question

目標

如果產品是報價並且價格最低，則返回特定列。

問題

我正在創建一個產品價格比較的應用程序。 我已經獲得了產品清單和特定產品的最低價格。 但是，在一天之內，產品可以設置為報價，並且具有所有其他產品的最低價格。 當發生這種情況時，我必須向用戶確認這樣的信息 - 帶有標志或類似的東西。

我正在考慮使用查詢本身來做這個行為 - 但我不知道，有時似乎這種做法是不一致的，因為如果產品沒有發售，不知道我將如何在C＃中處理這個問題等待productState列。 我需要建議（當然還有語法，因為我不知道[再次]）。

細節

我正在使用C＃.NET + MVC 4 + MySQL +實體框架5 +存儲過程+ Razor引擎。

以下片段返回產品清單的最低價格以進行比較：

Min(Case When marketProducts.ProductPromotionalPrice = 0
    Then 
       marketProducts.ProductOriginalPrice 
    Else
       Least(
        marketProducts.ProductPromotionalPrice,
        marketProducts.ProductOriginalPrice
       )End) As minProductPrice,

但是，我想做這樣的事情（當然 - 語法錯誤，但“工作”來說明）：

Min(Case When marketProducts.ProductPromotionalPrice = 0
    Then 
       marketProducts.ProductOriginalPrice 
    Else
       marketProducts.ProductState = 1 As productState, /* 
                                                           This is a normal
                                                           column.
                                                           1 means that 
                                                           the product is on 
                                                           offer.
                                                        */
       Least(
        marketProducts.ProductPromotionalPrice,
        marketProducts.ProductOriginalPrice
       )End) As minProductPrice,

完整查詢：

CREATE DEFINER=`root`@`localhost` PROCEDURE `getProductsList`(IN `categoryId` INT, IN `productState` INT)
    LANGUAGE SQL
    NOT DETERMINISTIC
    CONTAINS SQL
    SQL SECURITY DEFINER
    COMMENT ''
BEGIN
    Select product.Id As productId,
        product.Name As productName,
        Min(Case When marketProducts.ProductPromotionalPrice = 0
            Then marketProducts.ProductOriginalPrice Else
            Least(marketProducts.ProductPromotionalPrice, marketProducts.ProductOriginalPrice)
            End) As minProductPrice,
            measure.Name As measureName,
            measure.Abbreviation As measureAbbreviation,
            productsImages.ProductImageThumbnail As thumbnailUrl,
            product.InMarketsQuantity as numberOfMarketsThatHaveThisProduct
    From bm_market_products as marketProducts
    Join bm_products As product On marketProducts.ProductId = product.Id
    Join bm_categories As category On product.CategoryId = category.Id
    Join bm_measures As measure On product.MeasureId = measure.Id
    Join bm_products_images As productsImages On product.Id = productsImages.ProductId
    WHERE (productState Is Null Or marketProducts.ProductState = productState)
    And (categoryId Is Null Or category.Id = categoryId)
    Group By marketProducts.ProductId;
END

此過程返回以下內容：

有任何想法嗎？

Answer 1

你的語法錯誤的原因是你有時在一個空格中填充兩列。 解決方案是始終具有如下所示的兩列：

Select product.Id As productId,
    product.Name As productName,
    Min(Case When marketProducts.ProductPromotionalPrice = 0
        Then marketProducts.ProductOriginalPrice Else
        Least(marketProducts.ProductPromotionalPrice, marketProducts.ProductOriginalPrice)
        End) As minProductPrice,
    Min(Case When marketProducts.ProductPromotionalPrice = 0
            and marketProducts.ProductPromotionalPrice < marketProducts.ProductOriginalPrice
        Then 0 Else 1
        End) As productState,
        measure.Name As measureName,
        measure.Abbreviation As measureAbbreviation,
        productsImages.ProductImageThumbnail As thumbnailUrl,
        product.InMarketsQuantity as numberOfMarketsThatHaveThisProduct
From bm_market_products as marketProducts
Join bm_products As product On marketProducts.ProductId = product.Id
Join bm_categories As category On product.CategoryId = category.Id
Join bm_measures As measure On product.MeasureId = measure.Id
Join bm_products_images As productsImages On product.Id = productsImages.ProductId
WHERE (productState Is Null Or marketProducts.ProductState = productState)
And (categoryId Is Null Or category.Id = categoryId)
Group By marketProducts.ProductId;