Mysql - SELECT WITH ROLLUP

The WITH ROLLUP modifier adds extra rows to the resultset that represent super-aggregate summaries. The super-aggregated column is represented by a NULL value. Multiple aggregates over different columns will be added if there are multiple GROUP BY columns.

The LIMIT clause can be used at the same time, and is applied after the WITH ROLLUP rows have been added.

WITH ROLLUP cannot be used with ORDER BY. Some sorting is still possible by using ASC or DESC clauses with the GROUP BY column, although the super-aggregate rows will always be added last.

Examples

These examples use the following sample table

CREATE TABLE booksales ( 
  country VARCHAR(35), genre ENUM('fiction','non-fiction'), year YEAR, sales INT);

INSERT INTO booksales VALUES
  ('Senegal','fiction',2014,12234), ('Senegal','fiction',2015,15647),
  ('Senegal','non-fiction',2014,64980), ('Senegal','non-fiction',2015,78901),
  ('Paraguay','fiction',2014,87970), ('Paraguay','fiction',2015,76940),
  ('Paraguay','non-fiction',2014,8760), ('Paraguay','non-fiction',2015,9030);

The addition of the WITH ROLLUP modifier in this example adds an extra row that aggregates both years:

SELECT year, SUM(sales) FROM booksales GROUP BY year;
+------+------------+
| year | SUM(sales) |
+------+------------+
| 2014 |     173944 |
| 2015 |     180518 |
+------+------------+
2 rows in set (0.08 sec)

SELECT year, SUM(sales) FROM booksales GROUP BY year WITH ROLLUP;
+------+------------+
| year | SUM(sales) |
+------+------------+
| 2014 |     173944 |
| 2015 |     180518 |
| NULL |     354462 |
+------+------------+

In the following example, each time the genre, the year or the country change, another super-aggregate row is added:

SELECT country, year, genre, SUM(sales) 
  FROM booksales GROUP BY country, year, genre;
+----------+------+-------------+------------+
| country  | year | genre       | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2014 | fiction     |      87970 |
| Paraguay | 2014 | non-fiction |       8760 |
| Paraguay | 2015 | fiction     |      76940 |
| Paraguay | 2015 | non-fiction |       9030 |
| Senegal  | 2014 | fiction     |      12234 |
| Senegal  | 2014 | non-fiction |      64980 |
| Senegal  | 2015 | fiction     |      15647 |
| Senegal  | 2015 | non-fiction |      78901 |
+----------+------+-------------+------------+

SELECT country, year, genre, SUM(sales) 
  FROM booksales GROUP BY country, year, genre WITH ROLLUP;
+----------+------+-------------+------------+
| country  | year | genre       | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2014 | fiction     |      87970 |
| Paraguay | 2014 | non-fiction |       8760 |
| Paraguay | 2014 | NULL        |      96730 |
| Paraguay | 2015 | fiction     |      76940 |
| Paraguay | 2015 | non-fiction |       9030 |
| Paraguay | 2015 | NULL        |      85970 |
| Paraguay | NULL | NULL        |     182700 |
| Senegal  | 2014 | fiction     |      12234 |
| Senegal  | 2014 | non-fiction |      64980 |
| Senegal  | 2014 | NULL        |      77214 |
| Senegal  | 2015 | fiction     |      15647 |
| Senegal  | 2015 | non-fiction |      78901 |
| Senegal  | 2015 | NULL        |      94548 |
| Senegal  | NULL | NULL        |     171762 |
| NULL     | NULL | NULL        |     354462 |
+----------+------+-------------+------------+

The LIMIT clause, applied after WITH ROLLUP:

SELECT country, year, genre, SUM(sales) 
  FROM booksales GROUP BY country, year, genre WITH ROLLUP LIMIT 4;
+----------+------+-------------+------------+
| country  | year | genre       | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2014 | fiction     |      87970 |
| Paraguay | 2014 | non-fiction |       8760 |
| Paraguay | 2014 | NULL        |      96730 |
| Paraguay | 2015 | fiction     |      76940 |
+----------+------+-------------+------------+

Sorting by year descending:

SELECT country, year, genre, SUM(sales) 
  FROM booksales GROUP BY country, year DESC, genre WITH ROLLUP;
+----------+------+-------------+------------+
| country  | year | genre       | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2015 | fiction     |      76940 |
| Paraguay | 2015 | non-fiction |       9030 |
| Paraguay | 2015 | NULL        |      85970 |
| Paraguay | 2014 | fiction     |      87970 |
| Paraguay | 2014 | non-fiction |       8760 |
| Paraguay | 2014 | NULL        |      96730 |
| Paraguay | NULL | NULL        |     182700 |
| Senegal  | 2015 | fiction     |      15647 |
| Senegal  | 2015 | non-fiction |      78901 |
| Senegal  | 2015 | NULL        |      94548 |
| Senegal  | 2014 | fiction     |      12234 |
| Senegal  | 2014 | non-fiction |      64980 |
| Senegal  | 2014 | NULL        |      77214 |
| Senegal  | NULL | NULL        |     171762 |
| NULL     | NULL | NULL        |     354462 |
+----------+------+-------------+------------+