Combining UNION ALL and ORDER BY in Firebird

Question

This is my first attempt at answering my own question, since someone may well run into this and so it might be of help. Using Firebird, I want to combine the results of two queries using UNION ALL, then sort the resulting output on a given column. Something like:

(select C1, C2, C3 from T1)
union all 
(select C1, C2, C3 from T2)
order by C3

The parentheses came from valid syntax for other databases, and are needed to make sure the arguments to UNION ALL (an operation that's defined to work on tables - i.e. an unordered set of records) don't try to be ordered individually. However I couldn't get this syntax to work in Firebird - how can it be done?

score 29 · Accepted Answer · answered Dec 09 '08 at 21:08

29

SELECT C1, C2, C3
FROM (
    select C1, C2, C3 from T1
    union all 
    select C1, C2, C3 from T2
)
order by C3

answered Dec 09 '08 at 21:08

Cade Roux

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Note that this query requires Firebird 2.x or higher – alldayremix Jun 15 '16 at 16:03

score 12 · Answer 2 · answered Dec 09 '08 at 22:18

12

Field names are not required to be equal. That's why you can't use the field name in the order by.
You may use the field index instead. As in:

(select C1, C2, C3 from T1)
union all 
(select C7, C8, C9 from T2)
order by 3

answered Dec 09 '08 at 22:18

Douglas Tosi

2,232
2
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As written this requires Firebird 2.x, but if you remove the parentheses this will also work in Firebird 1.5 – alldayremix Jun 15 '16 at 16:02

score 7 · Answer 3 · edited Jun 23 '15 at 16:03

7

How about:

select C1, C2, C3 from T1
union all 
select C1, C2, C3 from T2
order by 2

At least in the newer Firebird Versions it works if you order by "Number" instead of using an Alias.

edited Jun 23 '15 at 16:03

josliber

41,865
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answered Jun 23 '15 at 15:15

KCM

71
1
1

score 2 · Answer 4 · answered Feb 03 '09 at 14:48

2

In Firebird 1.5 this works for me

create view V1 (C1, C2, C3) as
  select C1, C2, C3 from T1
  union all 
  select C1, C2, C3 from T2

and then

select C1, C2, C3 from V1 order by C3

answered Feb 03 '09 at 14:48

Tiago Moraes

318
2
7

+1 for "backwards" compatibility, the other answers doesn't work in Firebird 1.5 – Eliseo Ocampos Jul 17 '09 at 18:35
@Chris This is the same answer as Chris' one. You should delete yours or improve Chris' answer ;) – bluish Dec 16 '14 at 10:07

score 1 · Answer 5 · answered Dec 09 '08 at 21:02

1

Perform the UNION ALL in a view (without the ORDER BY clause), then select from the view using ORDER BY.

answered Dec 09 '08 at 21:02

Chris

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+1 for "backwards" compatibility, the other answers doesn't work in Firebird 1.5 – Eliseo Ocampos Jul 17 '09 at 18:34

score 0 · Answer 6 · answered Apr 17 '17 at 21:59

0

Moving order by into a query tail has no effect to output datagrid.

select * from (
    select first 1
        C1
    from T1
    order by id desc
)
union all
select * from (
    select first 1
        C1
    from T2
    order by id desc
)

answered Apr 17 '17 at 21:59

kai3341

29
3

Combining UNION ALL and ORDER BY in Firebird

6 Answers6

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