mysql - mysql查询分组依据

Question

以下查询为每次出现 recipecomments.RecipeID 带来一条记录，我只想为每个 recipeID 带来一条记录，按 recipeid 分组似乎不起作用

SELECT recipecomments.RecipeID
      ,recipecomments.CommentID 
      ,recipes.RecipeID
      ,recipes.Name
      ,recipes.CategoryID
      ,recipes.RatingTotal
      ,recipes.ImageMed
FROM recipecomments 
     JOIN recipes ON recipecomments.RecipeID = recipes.RecipeID                 
ORDER BY recipecomments.CommentID

Answer 1

如果您按recipid 分组，您需要决定要显示哪个CommentID。从你的语法来看，我猜是最高的。

 SELECT 
      recipecomments.RecipeID,
      MAX(recipecomments.CommentID),
      recipes.RecipeID,
      recipes.Name, 
      recipes.CategoryID,
      recipes.RatingTotal,
      recipes.ImageMed
 FROM recipecomments   
                JOIN recipes ON recipecomments.RecipeID = recipes.RecipeID 
 group by 
      recipecomments.RecipeID,
      recipes.RecipeID,
      recipes.Name, 
      recipes.CategoryID,
      recipes.RatingTotal,
      recipes.ImageMed