Question

我在本地服务器上有一个MySQL数据库。我使用PHP和JSON通过HTTP从MySQL数据库中获取数据。在Android应用程序中，使用JSON结果填充SQLite数据库。我已经验证了SQLite数据库实际上是通过运行类似于

的测试查询来填充的

Cursor cursor = database.rawQuery("SELECT recipe_id, ingredient_id, name FROM mm_ingredient_in_recipe_groups", null);

然后迭代生成的光标以查看数据是否存在。存在的数据存储在三个表中：

mm_ingredients，含有食谱成分。
mm_recipes，包含食谱数据。
mm_ingredient_in_recipe，其中包含用于加入mm_recipes和mm_ingredients中数据的数据（即解决多对多关系）。

我想要做的是运行一个查询，为参数配方名称选择成分。这意味着我必须与mm_ingredients以及mm_ingredient_in_recipe一起加入mm_recipes。

我尝试过运行以下查询：

database.rawQuery("SELECT ingredient.name, ingredient.base_unit FROM mm_ingredients AS ingredient INNER JOIN mm_ingredient_in_recipe AS ir ON ir.ingredient_id = ingredient._id INNER JOIN mm_recipes AS recipe ON ir.recipe_id = recipe._id WHERE recipe.name = ?", new String[] {"Spicy tomatsuppe"});

返回一个空光标。但是，在我的MySQL数据库中，运行相应的查询

SELECT ingredient.name, ingredient.base_unit FROM mm_ingredients AS ingredient INNER JOIN mm_ingredient_in_recipe AS ir ON ir.ingredient_id = ingredient.id INNER JOIN mm_recipes AS recipe ON ir.recipe_id = recipe.id WHERE recipe.name = "Spicy tomatsuppe";

返回预期的数据。我在这做错了什么？似乎我运行的每个查询都可以正常工作，直到我开始包含INNER JOIN。（在SQLite中，id字段被命名为_id，据我所知应该是最佳实践。）

编辑：添加用于写入数据库的代码：

下面是我如何填充表mm_recipes的数据库的示例。它与其他两个表类似。我将JSONArray.optString()用于SQLite的TEXT数据类型，JSONArray.optInt()用于INTEGER，JSONArray.optDouble()用于REAL。

public static final String TABLE_NAME                       = "mm_recipes";
public static final String TABLE_NAME_IN_JSON               = "mm_recipes";

public static final String COLUMN_ID                        = "_id";
public static final String COLUMN_NAME                      = "name";
public static final String COLUMN_IN_APP                    = "in_app";
public static final String COLUMN_DIFFICULTY                = "difficulty";
public static final String COLUMN_TIME_CONSUMPTION_UPPER    = "time_consumption_upper";
public static final String COLUMN_TIME_CONSUMPTION_LOWER    = "time_consumption_lower";
public static final String COLUMN_PREPARATION_TIME          = "preparation_time";
public static final String COLUMN_PORTIONS                  = "portions";
public static final String COLUMN_PORTIONS_UNIT             = "portions_unit";
public static final String COLUMN_DESCRIPTION               = "description";
public static final String COLUMN_TIPS                      = "tips";
public static final String COLUMN_USE_INGREDIENT_GROUPS     = "use_ingredient_groups";

public static final void populateDatabase(SQLiteDatabase database, JSONObject databaseData) throws JSONException{

    JSONArray table_data = databaseData.optJSONArray(TABLE_NAME_IN_JSON);
    ContentValues contentValues = new ContentValues();

    for (int i = 0; i < table_data.length(); i++){
        JSONObject data = table_data.getJSONObject(i);

        contentValues.clear();

        contentValues.put(COLUMN_NAME,                      data.optString(COLUMN_NAME));
        contentValues.put(COLUMN_IN_APP,                    data.optInt(COLUMN_IN_APP));
        contentValues.put(COLUMN_DIFFICULTY,                data.optString(COLUMN_DIFFICULTY));
        contentValues.put(COLUMN_TIME_CONSUMPTION_UPPER,    data.optInt(COLUMN_TIME_CONSUMPTION_UPPER));
        contentValues.put(COLUMN_TIME_CONSUMPTION_LOWER,    data.optInt(COLUMN_TIME_CONSUMPTION_LOWER));
        contentValues.put(COLUMN_PREPARATION_TIME,          data.optInt(COLUMN_PREPARATION_TIME));
        contentValues.put(COLUMN_PORTIONS,                  data.optInt(COLUMN_PORTIONS));
        contentValues.put(COLUMN_PORTIONS_UNIT,             data.optString(COLUMN_PORTIONS_UNIT));
        contentValues.put(COLUMN_DESCRIPTION,               data.optString(COLUMN_DESCRIPTION));
        contentValues.put(COLUMN_TIPS,                      data.optString(COLUMN_TIPS));
        contentValues.put(COLUMN_USE_INGREDIENT_GROUPS,     data.optInt(COLUMN_USE_INGREDIENT_GROUPS));

        database.insert(TABLE_NAME, null, contentValues);
    }

}

作为参考，这里也是一个如何创建mm_recipe表的示例。在我的班级mm_recipe：

public static final String DATATYPE_ID                      = "INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL";
public static final String DATATYPE_NAME                    = "TEXT NOT NULL";
public static final String DATATYPE_IN_APP                  = "INTEGER DEFAULT 0";
public static final String DATATYPE_DIFFICULTY              = "TEXT NOT NULL";
public static final String DATATYPE_TIME_CONSUMPTION_UPPER  = "INTEGER NOT NULL";
public static final String DATATYPE_TIME_CONSUMPTION_LOWER  = "INTEGER NOT NULL";
public static final String DATATYPE_PREPARATION_TIME        = "INTEGER";
public static final String DATATYPE_PORTIONS                = "INTEGER NOT NULL";
public static final String DATATYPE_PORTIONS_UNIT           = "TEXT NOT NULL";
public static final String DATATYPE_DESCRIPTION             = "TEXT";
public static final String DATATYPE_TIPS                    = "TEXT";
public static final String DATATYPE_USE_INGREDIENT_GROUPS   = "INT";

/**Create table statement.*/
public static final String CREATE_TABLE = 
    "CREATE TABLE"                  + " " + TABLE_NAME                      + " (" +
    COLUMN_ID                       + " " + DATATYPE_ID                     + ", " +
    COLUMN_NAME                     + " " + DATATYPE_NAME                   + ", " +
    COLUMN_IN_APP                   + " " + DATATYPE_IN_APP                 + ", " +
    COLUMN_DIFFICULTY               + " " + DATATYPE_DIFFICULTY             + ", " +
    COLUMN_TIME_CONSUMPTION_UPPER   + " " + DATATYPE_TIME_CONSUMPTION_UPPER + ", " +
    COLUMN_TIME_CONSUMPTION_LOWER   + " " + DATATYPE_TIME_CONSUMPTION_LOWER + ", " +
    COLUMN_PREPARATION_TIME         + " " + DATATYPE_PREPARATION_TIME       + ", " +
    COLUMN_PORTIONS                 + " " + DATATYPE_PORTIONS               + ", " +
    COLUMN_PORTIONS_UNIT            + " " + DATATYPE_PORTIONS_UNIT          + ", " +
    COLUMN_DESCRIPTION              + " " + DATATYPE_DESCRIPTION            + ", " +
    COLUMN_TIPS                     + " " + DATATYPE_TIPS                   + ", " +
    COLUMN_USE_INGREDIENT_GROUPS    + " " + DATATYPE_USE_INGREDIENT_GROUPS  + ");";

在我的SQLiteOpenHelper课程中：

@Override
public void onCreate(SQLiteDatabase database) {
    database.execSQL(Table_mm_recipes.CREATE_TABLE);
    database.execSQL(Table_mm_ingredient_in_recipe.CREATE_TABLE);
    database.execSQL(Table_mm_ingredients.CREATE_TABLE);
}

Answer 1

事实证明这是（正如预期的）一些愚蠢的错误。我会把这个留在这里以防其他人犯同样的错误。

因为我每次都设置了代码来删除创建数据库中的所有内容，所以这样：

database.execSQL("DELETE FROM " + Table_mm_recipes.TABLE_NAME);
database.execSQL("DELETE FROM " + Table_mm_ingredient_in_recipe.TABLE_NAME);
database.execSQL("DELETE FROM " + Table_mm_ingredients.TABLE_NAME);

某种方式，数据发生了不好的事情。这样做没有多大意义，因为你可以创建数据库并在SQLiteOpenHelper.onCreate()插入数据并且没问题。如果您需要在设置任何版本控制之前更新数据，只需卸载并重新安装应用程序即可。然后，如果愿意，您可以在SQLiteOpenHelper.onUpgrade()销毁数据。我不确定如何数据搞砸了，但他们肯定是。

的奇怪之处在于，我仍然可以通过做一个简单的

看到数据库中有数据

Cursor cursor = database.rawQuery("SELECT recipe_id, ingredient_id, name FROM mm_ingredient_in_recipe_groups", null);

并从之前迭代该游标。我在INNER JOIN语句之前直接对所有表执行了此操作，但它们仍然无效。它可能与错误删除/创建数据库有关。

除此之外，上述所有代码都应该有效且有效。

在Android中的SQLite中使用INNER JOIN时出现问题

1 个答案: