是否可以在android数据库的文本字段中应用主键

Question

我创建了一个简单的表,其中包含人员的姓名和电子邮件ID.当我给出这样的创建查询时:

"create table contacts (name text not null, email text primary key not null);"

但这不起作用.我在运行时没有出现任何异常或错误,也没有主键正常工作.在使用SQLite浏览器浏览表时,我观察到只有四种数据类型:

是否可以仅对整数应用主键？如果我想要文本字段的主键是什么情况.谢谢.这是我使用的代码:

public class DBAdapter {

public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "name";
public static final String KEY_EMAIL = "email";
private static final String TAG = "DBAdapter";

private static final String DATABASE_NAME = "MyDB";
private static final String DATABASE_TABLE = "contacts";
private static final int DATABASE_VERSION = 2;

private static final String DATABASE_CREATE =
    "create table contacts (_id integer primary key autoincrement, "
    + "name text not null, email text not null);";

private final Context context;    

private DatabaseHelper DBHelper;
private SQLiteDatabase db;

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

private static class DatabaseHelper extends SQLiteOpenHelper 
{
    DatabaseHelper(Context context) 
    {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) 
    {
        try {
            db.execSQL(DATABASE_CREATE);    
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

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

//---opens the database---
public DBAdapter open() throws SQLException 
{
    db = DBHelper.getWritableDatabase();
    return this;
}

//---closes the database---    
public void close() 
{
    DBHelper.close();
}

//---insert a contact into the database---
public long insertContact(String name, String email) 
{
    ContentValues initialValues = new ContentValues();
    initialValues.put(KEY_NAME, name);
    initialValues.put(KEY_EMAIL, email);
    return db.insert(DATABASE_TABLE, null, initialValues);
}

//---deletes a particular contact---
public boolean deleteContact(long rowId) 
{
    return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}

//---retrieves all the contacts---
public Cursor getAllContacts() 
{
    return db.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_NAME,
            KEY_EMAIL}, null, null, null, null, null);
}

//---retrieves a particular contact---
public Cursor getContact(long rowId) throws SQLException 
{
    Cursor mCursor =
            db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID,
            KEY_NAME, KEY_EMAIL}, KEY_ROWID + "=" + rowId, null,
            null, null, null, null);
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;
}

//---updates a contact---
public boolean updateContact(long rowId, String name, String email) 
{
    ContentValues args = new ContentValues();
    args.put(KEY_NAME, name);
    args.put(KEY_EMAIL, email);
    return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
}
}

Answer 1

根据sqlite文档的常见问题,使用主键TEXT作为数据类型应该可行.

我使用了你的查询,就在这里,创建了表格.

CREATE TABLE contacts ( email text primary key not null, name text not null);

INSERT INTO contacts VALUES ('sample@email.com', 'sample')
INSERT INTO contacts VALUES ('people@email.com', 'sample')

现在这里出了问题.

当我再次跑这个

INSERT INTO contacts VALUES ('sample@email.com', 'sample')

什么都没发生,没有错误.但它没有更新记录.所以我得出结论数据完整性,但你没有得到任何关于失败的反馈.

Answer 2

如果无法插入值,SQLiteDatabase.insertOrThrow()应抛出异常.此外它的返回值,以及从一个SQLiteDatabase.insert()就是rowid插入行或-1如果失败.您应该在代码中选择任何这些替代方案.