Question

我的数据库正在运行，但我插入的所有记录都是为了检查目的，现在我想删除所有表并创建新表，所以我尝试通过更改版本来更新数据库。

我没有对创建表查询进行任何更改，但是我的外键约束失败（代码787）。

这是我的DBHelper课程：

private static final String DATABASE_NAME = "roomatesDB";
    // database version
    private static final int DATABASE_VERSION = 3;

    // tables name
    public static final String APARTMENT_TABLE = "apartment";
    public static final String ROOMATE_TABLE = "roomate";
    public static final String SHOPCART_TABLE = "shopcart";
    public static final String ITEMS_TABLE = "items";

    // common column
    public static final String APARTMENT_NUMBER_COLUMN = "apartmentNum";

    // roomates table columns
    public static final String FIRST_NAME_COLUMN = "firstName";
    public static final String LAST_NAME_COLUMN = "lastName";
    public static final String PHONE_NUMBER_COLUMN = "phoneNumber";

    // shop cart table columns
    public static final String NUMBER_COLUMN = "number";
    public static final String LIST_NAME_COLUMN = "name";

    // item table
    public static final String PRICE_COLUMN = "price";
    public static final String ITEM_NAME_COLUMN = "name";

    // query for creating roomate table
    public static final String CREATE_ROOMATE_TABLE = "CREATE TABLE "
            + ROOMATE_TABLE + "(" + FIRST_NAME_COLUMN + " TEXT, "
            + LAST_NAME_COLUMN + " TEXT, " + PHONE_NUMBER_COLUMN + " TEXT, "
            + APARTMENT_NUMBER_COLUMN + " INTEGER, "
            + "FOREIGN KEY(" + APARTMENT_NUMBER_COLUMN + ") REFERENCES "
            + APARTMENT_TABLE + "(apartmentNum) " + ")";

    // query for crating shop cart table
    public static final String CREATE_SHOPLIST_TABLE = "CREATE TABLE "
            + SHOPCART_TABLE + "(" + NUMBER_COLUMN + " INTEGER PRIMARY KEY,"
            + LIST_NAME_COLUMN + " TEXT, "
            + APARTMENT_NUMBER_COLUMN + " INTEGER, "
            + "FOREIGN KEY(" + APARTMENT_NUMBER_COLUMN + ") REFERENCES "
            + APARTMENT_TABLE + "(apartmentNum) " + ")";

    // query for creating shop item table
    public static final String CREATE_SHOPITEM_TABLE = "CREATE TABLE "
            + ITEMS_TABLE + "(" + ITEM_NAME_COLUMN + " TEXT,"
            + PRICE_COLUMN + " DOUBLE, "
            + NUMBER_COLUMN + " INT, "
            + "FOREIGN KEY(" + NUMBER_COLUMN + ") REFERENCES "
            + SHOPCART_TABLE + "(number) " + ")";

    // query for creating apartment table
    public static final String CREATE_APARTMENT_TABLE = "CREATE TABLE "
            + APARTMENT_TABLE + "(" + APARTMENT_NUMBER_COLUMN + " INTEGER PRIMARY KEY"
            + ")";


    public DBHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    public void onConfigure(SQLiteDatabase db) {
        super.onConfigure(db);
        db.setForeignKeyConstraintsEnabled(true);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_APARTMENT_TABLE);
        db.execSQL(CREATE_ROOMATE_TABLE);
        db.execSQL(CREATE_SHOPLIST_TABLE);
        db.execSQL(CREATE_SHOPITEM_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + APARTMENT_TABLE);
        db.execSQL("DROP TABLE IF EXISTS " + ROOMATE_TABLE);
        db.execSQL("DROP TABLE IF EXISTS " + SHOPCART_TABLE);
        db.execSQL("DROP TABLE IF EXISTS " + ITEMS_TABLE);

        onCreate(db);

    }

Answer 1

documentation说：

如果启用了外键约束，则在从数据库模式中删除表之前，DROP TABLE命令会执行隐式DELETE FROM命令。 [...]如果作为DROP TABLE命令的一部分执行的隐式DELETE FROM违反了任何直接外键约束，则会返回错误并且不会删除该表。

以正确的顺序删除数据，以便所有中间步骤都有效。或者只是禁用外部约束检查（db.setForeignKeyConstraintsEnabled()）。

尝试在android中更新sqlite数据库时出错

1 个答案: