的Android SQLite的查詢外鍵

Question

我有兩個型號

categories(id, name, slug) 
places(id, name, cat_id) 

時，我必須插入地點的詳細信息到數據庫中，我有一個類別slug字符串。所以我將需要查詢的類別ID和插入到地方category_id

DBAdapter.java

public class DBAdapter { 
    // Database and version 
    private static final String DATABASE_NAME = "nomad.db"; 
    private static final int DATABASE_VERSION = 2; 

    // Tables 
    public static final String TABLE_CATEGORIES = "categories"; 
    public static final String TABLE_PLACES = "places"; 
    public static final String TABLE_PHOTOS = "photos"; 

    // Table Columns 
    public static final String COLUMN_ID = "_id"; 
    public static final String COLUMN_NAME = "name"; 
    public static final String COLUMN_SLUG = "slug"; 
    public static final String COLUMN_ACTIVE = "active"; 

    public static final String COLUMN_DISTANCE = "distance"; 
    public static final String COLUMN_DAYS = "days"; 
    public static final String COLUMN_LAT = "latitude"; 
    public static final String COLUMN_LNG = "longitude"; 
    public static final String COLUMN_WEATHER = "weather"; 
    public static final String COLUMN_TODO = "todo"; 
    public static final String COLUMN_ABOUT = "about"; 

    public static final String COLUMN_URL = "url"; 
    public static final String COLUMN_COPY = "copyright"; 

    public static final String COLUMN_CAT_ID = "category_id"; 
    public static final String COLUMN_PLACE_ID = "place_id"; 

    // Table Queries 
    private static final String CREATE_CATEGORIES = "CREATE TABLE categories (_id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, slug TEXT, active BOOLEAN);"; 
    private static final String CREATE_PLACES = "CREATE TABLE places (_id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, slug TEXT, category_id INTEGER, distance TEXT, days TEXT, latitude TEXT, longitude TEXT, weather TEXT, todo TEXT, about TEXT);"; 
    private static final String CREATE_PHOTOS = "CREATE TABLE photos (_id INTEGER PRIMARY KEY AUTOINCREMENT, place_id INTEGER, url TEXT, copyright TEXT);"; 

    private final Context context; 
    private static DatabaseHelper DBHelper; 
    private SQLiteDatabase db; 

    public DBAdapter(Context ctx) { 
     this.context = ctx; 
     DBHelper = new DatabaseHelper(context); 
    } 

    private static class DatabaseHelper extends SQLiteOpenHelper { 

     public DatabaseHelper(Context context) { 
      super(context, DATABASE_NAME, null, DATABASE_VERSION); 
      // TODO Auto-generated constructor stub 
     } 

     @Override 
     public void onCreate(SQLiteDatabase database) { 
      database.execSQL(CREATE_CATEGORIES); 
      database.execSQL(CREATE_PLACES); 
      database.execSQL(CREATE_PHOTOS); 
     } 

     @Override 
     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
      Log.w("Nomad", "Upgrading database from version " + oldVersion 
        + " to " + newVersion + ", which will destroy all old data"); 
      db.execSQL("DROP TABLE IF EXISTS categories"); 
      db.execSQL("DROP TABLE IF EXISTS places"); 
      db.execSQL("DROP TABLE IF EXISTS photos"); 
      onCreate(db); 
     } 

    } 

    public DBAdapter open() throws SQLException { 
     db = DBHelper.getWritableDatabase(); 
     return this; 
    } 

    public void close() { 
     DBHelper.close(); 
    } 

    // Methods 

    // Categories 

    // Insert Category 
    public long insertCategory(String name, String slug) { 
     ContentValues initialValues = new ContentValues(); 
     initialValues.put(COLUMN_NAME, name); 
     initialValues.put(COLUMN_SLUG, name); 
     initialValues.put(COLUMN_ACTIVE, true); 
     return db.insert(TABLE_CATEGORIES, null, initialValues); 
    } 

    // Get Category ID by Slug 
    public int find_city_id(String slug) { 
     Cursor c = db.query(TABLE_CATEGORIES, new String[] { COLUMN_ID }, COLUMN_SLUG + "=" + "'" + slug + "'", null, null, null, null, null); 
     if (c.moveToFirst()) { 
      do{ 
       return Integer.parseInt(c.getString(0)); 
      } while (c.moveToNext()); 
     } 
     else 
      return -1; 
    } 


    // Places 
    public long insertPlace(String name, String slug, String distance, 
      String days, String latitude, String longitude, String weather, 
      String todo, String about, int category_id) { 
     ContentValues initialValues = new ContentValues(); 
     initialValues.put(COLUMN_NAME, name); 
     initialValues.put(COLUMN_SLUG, slug); 
     initialValues.put(COLUMN_DISTANCE, distance); 
     initialValues.put(COLUMN_DAYS, days); 
     initialValues.put(COLUMN_LAT, latitude); 
     initialValues.put(COLUMN_LNG, longitude); 
     initialValues.put(COLUMN_WEATHER, weather); 
     initialValues.put(COLUMN_TODO, todo); 
     initialValues.put(COLUMN_ABOUT, about); 
     return db.insert(TABLE_PLACES, null, initialValues); 
    } 

} 

Answer 1

首先創建列級約束。

final String CREATE_TABLE_STATE="CREATE TABLE booking_delivery (" 
    + "id    INTEGER ," 
    +"remark    TEXT, " 
    +"barcode   INTEGER REFERENCES customer_info(cust_barcode));";