Question

我是SQL新手，不明白为什么我的语句会像以前那样运行。在Android Room DAO中使用它，并返回不需要的结果。

我在两个表中有此样本数据：

我有这句话：

@Transaction
    @Query("Select Distinct Category.* " +
            "from Category " +
            "inner join Items on Category.ID = Items.Category " +
            "where IsExcluded = 0 " + 
            "order by lower( Category.Name ) asc")
    LiveData<List<CatViewWithItemList>> getCatViewWithItemListGlobal();

通过一个简单的POJO接收结果：

public class CatViewWithItemList  {

    @Embedded
    public Cat myCat;

    @Relation(parentColumn = "ID",
            entityColumn = "Category") public List<ItemS> ItemList;

问题： 我不明白结果：

为什么退回第5项？它应该被where子句排除。我的陈述中有错误吗？

MikeT构建了一个包含相同错误的示例应用程序：

（编辑：我现在放下了bool转换器，Room似乎没有它就可以解析布尔值）或者这可能是因为我死掉的布尔型简单类型转换器引起的？一和零实际上是布尔值的占位符：

@TypeConverter
    public Boolean fromInt(int value) {
        return value == 0 ? false : true;
    }

    @TypeConverter
    public int toInt(Boolean bValue) {
        if (bValue == false) {
            return 0;
        } else {
            return 1;
        }
    }

感谢您的阅读！

编辑：非常感谢@Angela。她的test建议sql语句很好，并且该行为是由sqlite的特殊性引起的，或者是由接收器pojo中的嵌入式关系引起的。有人对此有意见吗？

编辑： MikeT解释了为什么房间关系似乎无法实现我想做的事情-至少只要没有人提出异议即可。在回答中，他提供了一种替代方法。

Answer 1

我认为这可能是由于您死了的简单转换器或也许是如何定义项目实体（我将 boolean 用于 isexcluded ，并且它似乎不用转换器就可以正常工作）。

使用我的Items Entity版本：-

@Entity(foreignKeys = @ForeignKey(entity = Category.class,parentColumns = "id", childColumns = "category", onDelete =  CASCADE))
public class Items {
    @PrimaryKey(autoGenerate = true)
    private long id;
    private String category;
    private boolean isexcluded;


    public void setCategory(String category) {
        this.category = category;
    }

    public void setId(long id) {
        this.id = id;
    }

    public void setIsexcluded(boolean isexcluded) {
        this.isexcluded = isexcluded;
    }

    public String getCategory() {
        return this.category;
    }

    public long getId() {
        return this.id;
    }

    public boolean isIsexcluded() {
        return this.isexcluded;
    }
}

以及DAO的类别：-

@Dao
interface CategoryDAO {
    @Query("SELECT * FROM Category")
    List<Category> getAllcategories();

    @Query("SELECT DISTINCT Category.* " +
            "FROM CATEGORY " +
            "INNER JOIN ITEMS ON category.id = Items.category " +
            "WHERE isexcluded = 0 " +
            "ORDER BY lower(category.name)")
    List<Category> getSpeacial();

    @Query("SELECT DISTINCT Category.* " +
            "FROM CATEGORY " +
            "INNER JOIN ITEMS ON category.id = Items.category " +
            "WHERE isexcluded = 0 " +
            "ORDER BY lower(category.name)")
    List<CatViewWithItemList> getSpeacial2();

    @Insert
    public long[] insertCategory(Category... Category);
}

以及

new Thread(new Runnable() {
            @Override
            public void run() {
                //mRoomDB.categoryDao().insertCategory(initialCategories());
                //mRoomDB.itemsDAO().insertItem(initialItems());
                List<Category> categoryList = mRoomDB.categoryDao().getAllcategories();
                List<Items> itemsList = mRoomDB.itemsDAO().getAllItems();
                for (Category c: categoryList) {
                    Log.d("CATEGORY","Category is " + c.getName() + " refrence is " + c.getId());
                }
                for (Items i: itemsList) {
                    Log.d("ITEM","Item is " + i.getId() + " Category reference is " + i.getCategory() + " Is Excluded is " + Boolean.toString(i.isIsexcluded()));
                }
                List<Category> categoryList2 = mRoomDB.categoryDao().getSpeacial();
                for (Category c: categoryList2) {
                    Log.d("CATEGORY2","Category is " + c.getName() + " reference is " + c.getId());
                }
                List<CatViewWithItemList> catViewWithItemLists = mRoomDB.categoryDao().getSpeacial2();
                for (CatViewWithItemList cvwil: catViewWithItemLists) {
                    Log.d("CATVIEWITEM","Category = " + cvwil.myCat.getId() + " ID = " + cvwil.ItemList.get(0).getId() + " IsExcluded = " + Boolean.toString(cvwil.ItemList.get(0).isIsexcluded()));
                }
            }
        }).start();

并带有：-

public class CatViewWithItemList {

    @Embedded
    public Category myCat;

    @Relation(parentColumn = "id",
            entityColumn = "category")
    public List<Items> ItemList;
}

然后结果是（第一部分是基础数据（哦，所以我不能拼写第三：）））：-

2018-12-19 21:47:05.376 2109-2125/? D/CATEGORY: Category is firstname refrence is a
2018-12-19 21:47:05.377 2109-2125/? D/CATEGORY: Category is secondname refrence is b
2018-12-19 21:47:05.377 2109-2125/? D/CATEGORY: Category is thridname refrence is c
2018-12-19 21:47:05.377 2109-2125/? D/ITEM: Item is 1 Category reference is a Is Excluded is false
2018-12-19 21:47:05.377 2109-2125/? D/ITEM: Item is 2 Category reference is c Is Excluded is false
2018-12-19 21:47:05.377 2109-2125/? D/ITEM: Item is 3 Category reference is null Is Excluded is false
2018-12-19 21:47:05.377 2109-2125/? D/ITEM: Item is 4 Category reference is b Is Excluded is false
2018-12-19 21:47:05.377 2109-2125/? D/ITEM: Item is 5 Category reference is b Is Excluded is true
2018-12-19 21:47:05.378 2109-2125/? D/ITEM: Item is 6 Category reference is null Is Excluded is true

然后是两组结果：-

2018-12-19 21:47:05.379 2109-2125/? D/CATEGORY2: Category is firstname reference is a
2018-12-19 21:47:05.380 2109-2125/? D/CATEGORY2: Category is secondname reference is b
2018-12-19 21:47:05.380 2109-2125/? D/CATEGORY2: Category is thridname reference is c


2018-12-19 21:47:05.382 2109-2125/? D/CATVIEWITEM: Category = a ID = 1 IsExcluded = false
2018-12-19 21:47:05.382 2109-2125/? D/CATVIEWITEM: Category = b ID = 4 IsExcluded = false
2018-12-19 21:47:05.382 2109-2125/? D/CATVIEWITEM: Category = c ID = 2 IsExcluded = false

其他

我认为您的问题不在于查询，而是与 CatViewItemList 有关，因为无论查询后/查询后，您都在与所有与类别相关的项目填充项目列表（即我认为，将项目列表嵌入到类别中）。这确实让我感到困惑，因为您只真正想要特定的相关项（我只是在代码中抓到了第一个），例如cvwil.ItemList.get(0).isIsexcluded()，幸运的是4排在5之前，因此排除在外的内容为假。

我认为您也许应该从“项目”中解决这个问题，例如加入“类别”。像

SELECT * 
FROM Items 
JOIN Category ON Items.category = category.id
WHERE Items.isexcluded = 0 
ORDER BY category.name ASC;

我将更新gitHub上的代码以执行此操作（请注意，我已更改“类别”表，使其具有唯一的列名称为 categoryid 而不是id）。

现在是结果（请注意，添加了另一个类别，并且又颠倒了2个项目，即排除了第一个项目（id 7）为true，然后id 8为false）：-

2018-12-20 21:39:56.971 9136-9160/so53839431.so53839431roomrelationship D/CATEGORY: Category is firstname Category ID is a
2018-12-20 21:39:56.971 9136-9160/so53839431.so53839431roomrelationship D/CATEGORY: Category is secondname Category ID is b
2018-12-20 21:39:56.971 9136-9160/so53839431.so53839431roomrelationship D/CATEGORY: Category is thirdname Category ID is c
2018-12-20 21:39:56.971 9136-9160/so53839431.so53839431roomrelationship D/CATEGORY: Category is fourthname Category ID is d
2018-12-20 21:39:56.971 9136-9160/so53839431.so53839431roomrelationship D/ITEM: Item is 1 Category reference is a Is Excluded is false
2018-12-20 21:39:56.971 9136-9160/so53839431.so53839431roomrelationship D/ITEM: Item is 2 Category reference is c Is Excluded is false
2018-12-20 21:39:56.971 9136-9160/so53839431.so53839431roomrelationship D/ITEM: Item is 3 Category reference is null Is Excluded is false
2018-12-20 21:39:56.971 9136-9160/so53839431.so53839431roomrelationship D/ITEM: Item is 4 Category reference is b Is Excluded is false
2018-12-20 21:39:56.971 9136-9160/so53839431.so53839431roomrelationship D/ITEM: Item is 5 Category reference is b Is Excluded is true
2018-12-20 21:39:56.971 9136-9160/so53839431.so53839431roomrelationship D/ITEM: Item is 6 Category reference is null Is Excluded is true
2018-12-20 21:39:56.971 9136-9160/so53839431.so53839431roomrelationship D/ITEM: Item is 7 Category reference is d Is Excluded is true
2018-12-20 21:39:56.971 9136-9160/so53839431.so53839431roomrelationship D/ITEM: Item is 8 Category reference is d Is Excluded is false
2018-12-20 21:39:56.972 9136-9160/so53839431.so53839431roomrelationship D/ITEMWITHCAT: Item id =1 Category reference is a Is Excluded is false Referenced Category is a Referenced Category name is firstname
2018-12-20 21:39:56.972 9136-9160/so53839431.so53839431roomrelationship D/ITEMWITHCAT: Item id =2 Category reference is c Is Excluded is false Referenced Category is c Referenced Category name is thirdname
2018-12-20 21:39:56.972 9136-9160/so53839431.so53839431roomrelationship D/ITEMWITHCAT: Item id =4 Category reference is b Is Excluded is false Referenced Category is b Referenced Category name is secondname
2018-12-20 21:39:56.972 9136-9160/so53839431.so53839431roomrelationship D/ITEMWITHCAT: Item id =8 Category reference is d Is Excluded is false Referenced Category is d Referenced Category name is fourthname

Androd Room嵌入式关系忽略了条件

1 个答案:

其他