Question

I got this code in one of my methods. It should check if the string is already in the database and if it is the db entry gets updated. If it is not there I catch the exception and just create the entry.

String s="hallo";

try {
   Cursor c1 = dba.fetchSubject(s);
   dba.updateSubject(c1.getLong(c1.getColumnIndex(DbAdapter.KEY_ROWID)), s, t, r);
} catch (SQLException e){
   dba.createSubject(s, t, r);
}

The problem is fetchSubject allway throws an Exception.

I use a similar method to get a db entry by a rowId instead of a String, which is working:

public Cursor fetchSubject(long rowId) throws SQLException {
    Cursor mCursor = database.query(true, DATABASE_TABLE2, new String[] {
            KEY_ROWID, KEY_SUBJECT, KEY_TEACHER, KEY_ROOM}, KEY_ROWID 
            + "=" + rowId, null, null, null, null, null);
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;
}

The method called on top:

public Cursor fetchSubject(String subject) throws SQLException {
    Cursor mCursor = database.query(true, DATABASE_TABLE2, new String[] {
            KEY_ROWID, KEY_SUBJECT, KEY_TEACHER, KEY_ROOM}, KEY_SUBJECT 
            + "=" + subject, null, null, null, null, null);
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;
}

The error:

 sqlite returned: error code = 1, msg = no such column: hallo

I don’t know where my error is. Isn’t it possible to use a string at the selection parameter?

Answer 1

Try adding single quotes around hallo

String s = "'hallo'";

Essentially what you’re doing is telling your query: select blah blah blah from TABLE where subject = hallo. Since hallo isn’t surrounded by quotes, it is trying to find a variable / column with that name. When we surround it with quotes, we are saying that we are looking for the string within these quotes, rather than a variable.

Think of it like normal programming..

String s = hallo; 

is completely different than

String s = "hallo";