PostgreSQL - making first row show as total of other rows

Question

Is there any way to make first row be different then the rest, so it would show total sum of the appropriate columns?

For example:

      fruits|a|b|c
            


        

Answer 1

You can avoid a second full scan of the table with a CTE:

PostgreSQL 9.2 Schema:

create table basket(fruits text, a integer, b integer, c integer);
insert into basket(fruits, a, b, c) values('apples', 1, 1, 1),
                                          ('apples', 0, 1, 2),
                                          ('bananas', 1, 1, 2),
                                          ('oranges', 1, 1, 1);

Query:

with w as ( select fruits, sum(a) a, sum(b) b, sum(c) c
            from basket
            group by fruits )
select * from w union all select 'total', sum(a), sum(b), sum(c) from w

Results:

|  FRUITS | A | B | C |
-----------------------
| bananas | 1 | 1 | 2 |
| oranges | 1 | 1 | 1 |
|  apples | 1 | 2 | 3 |
|   total | 3 | 4 | 6 |

SQL Fiddle here

Answer 2

This is now possible in version 9.5 of Postgres:

PostgreSQL 9.5 Schema

CREATE TABLE basket(fruits text, a integer, b integer, c integer);
CREATE TABLE
INSERT INTO basket(fruits, a, b, c) values('apples', 1, 1, 1),
                                      ('apples', 0, 1, 2),
                                      ('bananas', 1, 1, 2),
                                      ('oranges', 1, 1, 1);

Query

SELECT coalesce(fruits,'total'), sum(a) a, sum(b) b, sum(c) c
FROM basket
GROUP BY ROLLUP((fruits))

Results

 fruits  | a | b | c
---------+---+---+---
 apples  | 1 | 2 | 3
 bananas | 1 | 1 | 2
 oranges | 1 | 1 | 1
 total   | 3 | 4 | 6

This ROLLUP is equivalent to using an expressions with GROUPING SETS:

SELECT fruits, sum(a) a, sum(b) b, sum(c) c
FROM basket
GROUP BY GROUPING SETS (fruits, ())

Each sublist in the GROUPING SETS is interpreted the same way as though it were directly in the GROUP BY clause.

Answer 3

SELECT 'total' AS fruits, sum(a), sum(b), sum(c) FROM basket
UNION ALL
SELECT fruits, sum(a), sum(b), sum(c) FROM basket GROUP BY fruits