Sqlite Verify If Value Of Column Exists

i'm wondering if this method is right to verify if the value of _username already exists in the column 'username' public boolean verification(String _username) throws SQLException{

Solution 1:

Beware of SQL injection attacks! You should always use a parameterized query:

Cursorc= dataBase.rawQuery("SELECT 1 FROM "+TABLE_NAME+" WHERE "+KEY_USERNAME+"=?", newString[] {_username});

(Honestly I'm not sure how your first query didn't throw an exception since you forgot to wrap the string in quotes...)

Also rawQuery() will always return a Cursor, you must check if the Cursor is empty, not null.

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As for "the best" approach, this works fine, but I recommend closing the Cursor to free up resources. All together:

publicbooleanverification(String _username) {
    Cursor c = dataBase.rawQuery("SELECT 1 FROM "+TABLE_NAME+" WHERE "+KEY_USERNAME+"=?", newString[] {_username});
    boolean exists = c.moveToFirst();
    c.close();
    return exists;
}

Solution 2:

Is there a better way to do the same thing, i'm really not sure about this, it seemed right for me. Thanks.

In the terms of security and purity yes, for sure.

publicbooleanverification(String _username)throws SQLException {
    intcount= -1;
    Cursorc=null; 
    try {
       Stringquery="SELECT COUNT(*) FROM " 
                   + TABLE_NAME + " WHERE " + KEY_USERNAME + " = ?"
       c = dataBase.rawQuery(query, newString[] {_username});
       if (c.moveToFirst()) {
          count = c.getInt(0);
       }
       return count > 0;
    }
    finally {
       if (c != null) {
          c.close();
       }
    }
}

I recommend you to an usage of ? that is called placeholder. Each placeholder will be replaced with value from string array in the same order. This is called also parametrized statement as a defence agains SQL injection. When your work with Cursor is finished, release it.