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我試圖插入引用許多朋友的費用。但是使用外鍵,它只能引用friendId,但是我想在費用表中存儲2個friendId而不是一個用於費用的朋友。因爲每個朋友都可以有很多開支,並且開支可以被很多朋友分享。我怎樣才能實現這種關係?也許不使用外鍵?任何人都可以給我這樣做的想法嗎?非常感謝。Android - (SQLite)外鍵一次引用多個ID
這是我創建的數據庫代碼:
public void onCreate(SQLiteDatabase database) {
String query, query1, query2, query3;
query = "CREATE TABLE events (eventId INTEGER PRIMARY KEY, eventName TEXT, eventDate TEXT, eventLocation TEXT, eventDescription TEXT);";
query1 = "CREATE TABLE friends (friendId INTEGER PRIMARY KEY, friendName TEXT, friendNumber TEXT, friendEmail TEXT, friendSpending DOUBLE, friendEvent INTEGER, FOREIGN KEY(friendEvent) REFERENCES events(eventId) ON DELETE CASCADE);";
query2 = "CREATE TABLE expenses (expenseId INTEGER PRIMARY KEY, expenseName TEXT, expenseType TEXT, expensePrice REAL, expenseQuantity INTEGER, expenseEvent INTEGER REFERENCES events(eventId) ON DELETE CASCADE, expenseFriend INTEGER REFERENCES friends(friendId) ON DELETE CASCADE);";
query3 = "CREATE TABLE temporary (_id INTEGER PRIMARY KEY, spendingId INTEGER)";
database.execSQL(query);
database.execSQL(query1);
database.execSQL(query2);
database.execSQL(query3);
Log.d(LOGCAT, "events Created");
Log.d(LOGCAT, "friends Created");
Log.d(LOGCAT, "expenses Created");
所以,當我想訪問數據,我該怎麼辦?選擇friendId還是expenseId? – AndroidWorld12
這取決於你想要選擇的數據:)我建議你去Google關於SQL連接語句 –