Question

I have been using the following code to query one table:

public Cursor fetchFilteredItemsNearSortedByDistance(String strTable, String[] strArrayFields, String strField, String strCriterion, double dblCentreEasting, double dblCentreNorthing, double dblRadius) {

  String strSQL = "Easting > " + Double.toString(dblCentreEasting-dblRadius);
  strSQL += " AND Easting < "  + Double.toString(dblCentreEasting+dblRadius);
  strSQL += " AND Northing > "  + Double.toString(dblCentreNorthing-dblRadius);
  strSQL += " AND Northing < "  + Double.toString(dblCentreNorthing+dblRadius);
  strSQL += " AND " + strField + " LIKE '%" + strCriterion + "%'";
  strSQL += " ORDER BY ";
  strSQL += "((Easting - " + Double.toString(dblCentreEasting)+")";
  strSQL += " * (Easting - " + Double.toString(dblCentreEasting)+")";
  strSQL += " + (Northing - " + Double.toString(dblCentreNorthing)+")";
  strSQL += " * (Northing - " + Double.toString(dblCentreNorthing)+"))";
  strSQL += " COLLATE NOCASE";

  return myDbHelper.myDataBase.query(strTable, strExtendedArrayFields, strSQL, null, null, null, null);     
}

The above code has been working satisfactorily. However, I now want to extend the idea to a UNION of two or more tables, and have tried the following code:

public Cursor fetchFilteredPOIsNearSortedByDistance(String strTable, String[] strArrayFields, String strField, String strCriterion, double dblCentreEasting, double dblCentreNorthing, double dblRadius) {

  String strSQL = "SELECT * FROM TableA ";
  strSQL += "UNION SELECT * FROM TableB ";
  strSQL += "WHERE ( Easting > " + Double.toString(dblCentreEasting-dblRadius);
  strSQL += " AND Easting < "  + Double.toString(dblCentreEasting+dblRadius);
  strSQL += " AND Northing > "  + Double.toString(dblCentreNorthing-dblRadius);
  strSQL += " AND Northing < "  + Double.toString(dblCentreNorthing+dblRadius);
  strSQL += " AND " + strField + " LIKE '%" + strCriterion + "%' ) ";
  strSQL += " ORDER BY ";
  strSQL += "((Easting - " + Double.toString(dblCentreEasting)+")";
  strSQL += " * (Easting - " + Double.toString(dblCentreEasting)+")";
  strSQL += " + (Northing - " + Double.toString(dblCentreNorthing)+")";
  strSQL += " * (Northing - " + Double.toString(dblCentreNorthing)+"))";
  strSQL += " COLLATE NOCASE";

  return myDbHelper.myDataBase.rawQuery(strSQL, null);
}

However, this produces a “SQLiteException: 1st ORDER BY term does not match any column in the result set” error.

The full error in LogCat is:

ERROR/AndroidRuntime(11444): Caused by: android.database.sqlite.SQLiteException: 1st ORDER BY term does not match any column in the result set: , while compiling: SELECT * FROM TableA UNION SELECT * FROM TableB WHERE ( Easting > 594378.8427734375 AND Easting < 663822.8427734375 AND Northing > 127586.046875 AND Northing < 197030.046875 AND Name LIKE '%%' )  ORDER BY ((Easting - 629100.8427734375) * (Easting - 629100.8427734375) + (Northing - 162308.046875) * (Northing - 162308.046875)) COLLATE NOCASE

Can anyone help me onto the right track, please?

Answer 1

I think I must have made some mistakes in the syntax of my SQL.

In simplified terms, the code which did not work was:

SELECT * FROM TableA UNION SELECT * FROM TableB
WHERE (FieldA > X1 AND FieldA < X2 AND FieldB > Y1 AND FieldB < Y2
AND FieldC LIKE '%Criterion%')
ORDER BY [Function of FieldA and FieldB] COLLATE NOCASE

I have now replaced this with:

SELECT FieldA, FieldB, FieldC, .... ,
[Function of FieldA and FieldB] AS CalculatedField
FROM TableA
WHERE FieldA BETWEEN X1 AND X2
AND FieldB BETWEEN Y1 AND Y2
AND FieldC LIKE '%Criterion%'
UNION
SELECT FieldA, FieldB, FieldC, .... ,
[Function of FieldA and FieldB] AS CalculatedField
FROM TableB
WHERE FieldA BETWEEN X1 AND X2
AND FieldB BETWEEN Y1 AND Y2
AND FieldC LIKE '%Criterion%'
ORDER BY CalculatedField COLLATE NOCASE

Although this SQL statement is much longer, it seems to work, and what is more is amazingly quick … the filtering on about 10,000 rows of data and sorting all happens in less than 50 milliseconds.