How can I have aggregate function and indivisual expression in same sql statement?

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If I use this query it will show result

SQL

select max(id),rno
from y
group by rno

MAX(ID)                       RNO

  3                               30
  4                               40
  1                               10
  6                               60

If I do not use GROUP BY then error occurs

SQL

select max(id),rno from y;
select max(id),rno from y

ERROR at line 1:<br />
ORA-00937: not a single-group group function

But I want result set as below(maximum of id)

 MAX(ID)
  6
 RNO
30
40
10
60

What sh'd I do???

Posted 25-May-13 0:06am

surkhi

Updated 25-May-13 8:21am

Maciej Los

v2

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Maciej Los · Accepted Answer · 2013-05-25T08:43:00

First of all, you need to undesrtand that MAX (aggregate function) returns maximum value as a single result row based on groups of rows, rather than on single rows. Of course, you can always get single row based on single column:

SQL

SELECT MAX(ID)
FROM y

but your query returns max id for each rno.

To get expected output, try this:

SQL

SELECT MAX(ID) AS [Values]
FROM y
UNION ALL
SELECT rno AS [Values]
FROM y

but you'll never know which value belongs to which column (id or rno).
To get description of values, try this:

SQL

SELECT 'max id' AS [Description], MAX(ID) AS [Values]
FROM y
UNION ALL
SELECT  'rno' AS [Description], rno AS [Values]
FROM y

Please, refer these:
group by (functions)[^]
aggregate functions[^]
UNION[^]