Sequel Pro Combine多条线，其中只有1列是不同的，但其余是相同的

Question

我有一张餐桌，有几个ID与主表上的其他表相关联。

我还有另外一张桌子，里面的食物成分是用ID列出的，所以我不必一遍又一遍地输入食材。但是，当我运行以下搜索时，我会得到用餐名称，多次列出，因为每种成分都列在它自己的行中。我怎样才能得到它显示的名称，然后在同一行上的所有成分？

SELECT 
    mealName, ingredient, quantity 
FROM 
    meals, mealTotal, ingredients 
WHERE 
     mealTotal.mealId = meals.MealId 
    and mealTotal.ingredientId = ingredients.ingredientId 
ORDER BY 
    mealName; 

目前显示：

Apple Pie Apple 1 
Apple Pie Tabantha Wheat 1 
Apple Pie Goat Butter  1 
Apple Pie Cane Sugar 1 

我想什么它显示：

Apple Pie Apple 1 Tabantha Wheat 1  Goat Butter 1 Cane Sugar 1 

Answer 1

您可以使用GROUP_CONCAT返回所有的成分和数量的清单。于是开始与现有的查询，你将其转换为：

-- Concatenate all your (ingredient, quantity) 
SELECT 
    mealName, 
    GROUP_CONCAT(ingredient_and_quantity ORDER BY ingredient_and_quantity SEPARATOR '\t') AS ingredient_list 
FROM 
    (SELECT 
     mealName, ingredient, quantity, 
     CONCAT(ingredient, ' ', quantity) AS ingredient_and_quantity 
    FROM 
     meals 
     JOIN mealTotal ON mealTotal.mealId = meals.mealId 
     JOIN ingredients ON ingredients.ingredientId = mealTotal.ingredientId 
    ) AS q 
ORDER BY 
    mealName; 

这将会给你一个字符串与所有的成分和相应量。

 
mealName | ingredient_list               
:-------- | :----------------------------------------------------------------------- 
Apple Pie | Apple 1  Cane Sugar 1  Goat Butter 1  Tabantha Wheat 1 

请注意，我已经改变了隐含JOIN s到明确的。 （隐含的JOIN s更难阅读且容易出错，很容易就会错过WHERE上的一个链接条件，并且您会得到一个您预期不到的carteasian产品）。

您可以在dbfiddle here

---

检查了这一切。如果你想有成份不同列(ingredient_1, quantity_1, ingredient_2, quantity_2, ...)，然后你可以从这个查询的变化开始的列表，并分解使用SUBSTRING_INDEX(str,delim,count)归组数据：

-- Pivot 
SELECT 
    mealName, 
    SUBSTRING_INDEX(SUBSTRING_INDEX(ingredients, ',', 1), ',', -1) AS ingredient_1, 
    SUBSTRING_INDEX(SUBSTRING_INDEX(ingredients, ',', 2), ',', -1) AS ingredient_2, 
    SUBSTRING_INDEX(SUBSTRING_INDEX(ingredients, ',', 3), ',', -1) AS ingredient_3, 
    SUBSTRING_INDEX(SUBSTRING_INDEX(ingredients, ',', 4), ',', -1) AS ingredient_4, 

    SUBSTRING_INDEX(SUBSTRING_INDEX(quantities, ',', 1), ',', -1) AS quantity_1, 
    SUBSTRING_INDEX(SUBSTRING_INDEX(quantities, ',', 2), ',', -1) AS quantity_2, 
    SUBSTRING_INDEX(SUBSTRING_INDEX(quantities, ',', 3), ',', -1) AS quantity_3, 
    SUBSTRING_INDEX(SUBSTRING_INDEX(quantities, ',', 4), ',', -1) AS quantity_4 
FROM 
    (SELECT 
     mealName, 
     GROUP_CONCAT(ingredient ORDER BY ingredient SEPARATOR ',') AS ingredients, 
     GROUP_CONCAT(quantity ORDER BY ingredient SEPARATOR ',') AS quantities 
    FROM 
     (SELECT 
      mealName, ingredient, quantity 
     FROM 
      meals 
      JOIN mealTotal ON mealTotal.mealId = meals.mealId 
      JOIN ingredients ON ingredients.ingredientId = mealTotal.ingredientId 
     ORDER BY 
      mealName, ingredient 
     ) AS q 
    ) AS q2 
ORDER BY 
    mealName; 

这将使你喜欢的东西：

 
mealName | ingredient_1 | ingredient_2 | ingredient_3 | ingredient_4 | quantity_1 | quantity_2 | quantity_3 | quantity_4 
:-------- | :----------- | :----------- | :----------- | :------------- | :--------- | :--------- | :--------- | :--------- 
Apple Pie | Apple  | Cane Sugar | Goat Butter | Tabantha Wheat | 1.01  | 1.04  | 1.03  | 1.02  

您可以在dbfiddle here

注意检查这，这不缩放（如果你需要10列，你必须用手工做的话），而一些值可能重复一次，因为STRING_INDEX的工作方式。我不会推荐这种方法。