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# Query to find a missing number

Hello,

I need to write a query to find out a set of missing number in a given
sequence.

Eg : a Column in some table has the following data

Col1

1

2

3

4

5

6

8

9

10

Here I need to write a query to find out that number 7 is missing in the
given sequence.

One possible solution is by using any loop. But I am looking out if the same
can be achieved using any query.

Regards,

Mahesh

Jul 13 '06 #1
4 25497
Mahesh BS wrote:
>Hello,
I need to write a query to find out a set of missing number in a given
sequence.
Eg : a Column in some table has the following data
Col1
1
2
3
4
5
6
8
9
10
Here I need to write a query to find out that number 7 is missing in the
given sequence.
One possible solution is by using any loop. But I am looking out if the same
can be achieved using any query.
Regards,
Mahesh
after some tests, i am arrived to this:

select (a.col1 + 1)
from tab1 a
where not exists
(select 1
from tab1 b
where b.col1 = (a.col1 + 1))
and a.col1 not in
(select max(c.col1)
from tab1 c)
order by 1

try it!
fabio

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f.

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Jul 13 '06 #2
On Thu, 13 Jul 2006 21:43:21 +0530, Mahesh BS wrote:
>

Hello,

I need to write a query to find out a set of missing number in a given
sequence.
Hi Mahesh,

Check out http://www.aspfaq.com/show.asp?id=2516, under the heading
"Finding IDENTITY gaps".

--
Hugo Kornelis, SQL Server MVP
Jul 13 '06 #3
>I need to write a query to find out a set of missing number in a given sequence.<<
Here is a classix version of this problem:

Let's assume we have a table of people who bought tickets that are
supposed to be in sequential order and we want to make a list of what
is missing in each buyer's set of tickets.

CREATE TABLE Tickets
ticket_nbr INTEGER DEFAULT 1 NOT NULL
CHECK (ticket_nbr 0),

INSERT INTO Tickets VALUES ('a', 2);
INSERT INTO Tickets VALUES ('a', 3);
INSERT INTO Tickets VALUES ('a', 4);
INSERT INTO Tickets VALUES ('b', 4);
INSERT INTO Tickets VALUES ('c', 1);
INSERT INTO Tickets VALUES ('c', 2);
INSERT INTO Tickets VALUES ('c', 3);
INSERT INTO Tickets VALUES ('c', 4);
INSERT INTO Tickets VALUES ('c', 5);
INSERT INTO Tickets VALUES ('d', 1);
INSERT INTO Tickets VALUES ('d', 6);
INSERT INTO Tickets VALUES ('d', 7);
INSERT INTO Tickets VALUES ('d', 9);
INSERT INTO Tickets VALUES ('e', 10);

If we can assume that there is a relatively small number of Tickets,
then you could use a table of sequential numbers from 1 to (n) and
write:

FROM Tickets AS T1, Sequence AS S1
WHERE seq <= (SELECT MAX(ticket_nbr) -- set the range
FROM Tickets AS T2
AND seq NOT IN (SELECT ticket_nbr -- get missing numbers
FROM Tickets AS T3

Another version:

BEGIN
SELECT *
INTO #foobar
FROM Tickets
UNION ALL
FROM Tickets;

(T1.ticket_nbr + 1) AS gap_start,
(MIN(T2.ticket_ nbr) - 1) AS gap_end
FROM --Tickets AS T1,
#foobar AS T1,
Tickets AS T2
WHERE T1.ticket_nbr < T2.ticket_nbr
HAVING MIN(T2.ticket_n br) - T1.ticket_nbr 1;

END;

The trick here is to add a zero to act as a boundary when 1 is missing
from the sequence.

In Standard SQL-92, you could write the UNION ALL expression directly
in the FROM clause.

Jul 15 '06 #4
BEGIN
SELECT *
INTO #foobar
FROM Tickets
UNION ALL
FROM Tickets;
Does this mean when other people use temporary tables (like you've just
done) then they aren't going to get a bashing for 'procedural programming'
and imiatating a magentic tape file system?

Perhaps you've finally woke up to writing SQL for production rather than for
a book!

--
Tony Rogerson
SQL Server MVP
http://sqlblogcasts.com/blogs/tonyrogerson - technical commentary from a SQL
Server Consultant
http://sqlserverfaq.com - free video tutorials
news:11******** **************@ m79g2000cwm.goo glegroups.com.. .
>
>>I need to write a query to find out a set of missing number in a given
sequence.<<

Here is a classix version of this problem:

Let's assume we have a table of people who bought tickets that are
supposed to be in sequential order and we want to make a list of what
is missing in each buyer's set of tickets.

CREATE TABLE Tickets
ticket_nbr INTEGER DEFAULT 1 NOT NULL
CHECK (ticket_nbr 0),

INSERT INTO Tickets VALUES ('a', 2);
INSERT INTO Tickets VALUES ('a', 3);
INSERT INTO Tickets VALUES ('a', 4);
INSERT INTO Tickets VALUES ('b', 4);
INSERT INTO Tickets VALUES ('c', 1);
INSERT INTO Tickets VALUES ('c', 2);
INSERT INTO Tickets VALUES ('c', 3);
INSERT INTO Tickets VALUES ('c', 4);
INSERT INTO Tickets VALUES ('c', 5);
INSERT INTO Tickets VALUES ('d', 1);
INSERT INTO Tickets VALUES ('d', 6);
INSERT INTO Tickets VALUES ('d', 7);
INSERT INTO Tickets VALUES ('d', 9);
INSERT INTO Tickets VALUES ('e', 10);

If we can assume that there is a relatively small number of Tickets,
then you could use a table of sequential numbers from 1 to (n) and
write:

FROM Tickets AS T1, Sequence AS S1
WHERE seq <= (SELECT MAX(ticket_nbr) -- set the range
FROM Tickets AS T2
AND seq NOT IN (SELECT ticket_nbr -- get missing numbers
FROM Tickets AS T3

Another version:

BEGIN
SELECT *
INTO #foobar
FROM Tickets
UNION ALL
FROM Tickets;

(T1.ticket_nbr + 1) AS gap_start,
(MIN(T2.ticket_ nbr) - 1) AS gap_end
FROM --Tickets AS T1,
#foobar AS T1,
Tickets AS T2
WHERE T1.ticket_nbr < T2.ticket_nbr
HAVING MIN(T2.ticket_n br) - T1.ticket_nbr 1;

END;

The trick here is to add a zero to act as a boundary when 1 is missing
from the sequence.

In Standard SQL-92, you could write the UNION ALL expression directly
in the FROM clause.

Jul 17 '06 #5

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