How to search alphanumeric value using sqlite db in android

I saved alphanumeric value in sqlite db,But edittext alphanumeric value enter not compare to sqlite db.this problem please suggestion.this is my code here .. example:this value search(emp_01)

open.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub              
            datab=mdb.getWritableDatabase();                
            c=datab.rawQuery("select * from demo where PATIENT_ID="+search_id.getText().toString()+";",null);
            if(c!=null && c.getCount()>0)
            {
                  c.moveToFirst();
                    do {
                        String cc = c.getString(0);
                        Toast.makeText(getBaseContext(), ""+cc, 100).show();
                    } while (c.moveToNext());
            }           
        }
    });