/**
     * Return a new Table whose columns are COLUMNNAMES, selected from pairs of
     * rows from this table and from TABLE2 that match on all columns with
     * identical names and satisfy CONDITIONS.
     */
    Table select(Table table2, List<String> columnNames,
            List<Condition> conditions) {
        Table result = new Table(columnNames);

        ArrayList<String> commonNames =
            new ArrayList<String>(this.columnTitles);
        commonNames.retainAll(table2.columnTitles);

        ArrayList<Column> common1 = new ArrayList<Column>();
        ArrayList<Column> common2 = new ArrayList<Column>();
        for (String name : commonNames) {
            common1.add(new Column(name, this));
            common2.add(new Column(name, table2));

        }

        ArrayList<Column> outCols = new ArrayList<Column>();
        for (String colName : columnNames) {
            outCols.add(new Column(colName, this, table2));
        }

        for (Row rowT1 : this._rows) {
            for (Row rowT2 : table2._rows) {
                if (equijoin(common1, common2, rowT1, rowT2)) {
                    if (testConditions(conditions,
                        new Row[] { rowT1, rowT2 })) {
                        Row newRow = new Row(outCols, rowT1, rowT2);
                        result.add(newRow);
                    }
                }
            }
        }

        return result;
    }

    /**
     * Return true if the columns COMMON1 from ROW1 and COMMON2 from ROW2 all
     * have identical values. Assumes that COMMON1 and COMMON2 have the same
     * number of elements and the same names, that the columns in COMMON1 apply
     * to this table, those in COMMON2 to another, and that ROW1 and ROW2 come,
     * respectively, from those tables.
     */
    private static boolean equijoin(List<Column> common1, List<Column> common2,
            Row row1, Row row2) {

        for (int i = 0; i < common1.size(); i++) {
            String v1 = common1.get(i).getFrom(row1);
            String v2 = common2.get(i).getFrom(row2);
            if (!v1.equals(v2)) {
                return false;
            }
        }
        return true;
    }