In DB2, I have this query to list numbers 1-x:
select level from SYSIBM.SYSDUMMY1 connect by level <= "some number"
But this maxes out due to SQL20450N Recursion limit exceeded within a hierarchical query.
How can I generate a list of numbers between 1 and x using a select statement when x is not known at runtime?
I found an answer based on this post:
WITH d AS
(SELECT LEVEL - 1 AS dig FROM SYSIBM.SYSDUMMY1 CONNECT BY LEVEL <= 10)
SELECT t1.n
FROM (SELECT (d7.dig * 1000000) +
(d6.dig * 100000) +
(d5.dig * 10000) +
(d4.dig * 1000) +
(d3.dig * 100) +
(d2.dig * 10) +
d1.dig AS n
FROM d d1
CROSS JOIN d d2
CROSS JOIN d d3
CROSS JOIN d d4
CROSS JOIN d d5
CROSS JOIN d d6
CROSS JOIN d d7) t1
JOIN ("subselect that returns desired value as i") t2
ON t1.n <= t2.i
ORDER BY t1.n
That's how I usually create lists:
For your example
numberlist (num) as
(
select min(1) from anytable
union all
select num + 1 from numberlist
where num <= x
)
I did something like this when I wanted a list of values to correspond with months:
with t1 (mon) as (
values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12)
)
select * from t1
It seems a bit kludgy, but for a small list like 1-12, or even 1-50, it did what I needed it to.
It's nice to see someone else tagging their questions with DB2.
If you have any table known to have more than x rows, you can always do:
select * from (
select row_number() over () num
from my_big_table
) where num <= x
or, per bhamby's suggestion:
select row_number() over () num
from my_big_table
fetch first X rows only
For DB2 you can use recursive common table expressions (cf. IBM documentation on recursive CTE):
with max(num) as (
select 1 from sysibm.sysdummy1
)
,result (num) as (
select num from max
union ALL
select result.num+1
from result
where result.num<=100
)
select * from result;
Related
generate_series function on Redshift works as expected, when used in a simple select statement.
WITH series AS (
SELECT n as id from generate_series (-10, 0, 1) n
) SELECT * FROM series;
-- Works fine
As soon as I add a JOIN condition, redshift throws
com.amazon.support.exceptions.ErrorException: Function
generate_series(integer,integer,integer)" not supported"
DROP TABLE testing;
CREATE TABLE testing (
id INT
);
WITH series AS (
SELECT n as id from generate_series (-10, 0, 1) n
) SELECT * FROM series S JOIN testing T ON S.id = T.id;
-- Function "generate_series(integer,integer,integer)" not supported.
Redshift Version
SELECT version();
-- PostgreSQL 8.0.2 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.4.2 20041017 (Red Hat 3.4.2-6.fc3), Redshift 1.0.1485
Are there any workarounds to make this work?
generate_series is not supported by Redshift. It works only standalone on a leader node.
A workaround would be using row_number against any table that has sufficient number of rows:
with
series as (
select (row_number() over ())-11 from some_table limit 10
) ...
also, this question was asked multiple times already
You are correct that this does not work on Redshift.
See here.
The easiest workaround is to create a permanent table "manually" beforehand with the values within that table, e.g. you could have rows on that table for -1000 to +1000, then select the range from that table,
So for your example you would have something like
WITH series AS (
SELECT n as id from (select num as n from newtable where num between -10 and 0) n
) SELECT * FROM series S JOIN testing T ON S.id = T.id;
Does that work for you?
Alternatively, if you cannot create the table beforehand or prefer not to, you could use something like this
with ten_numbers as (select 1 as num union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9 union select 0)
,generted_numbers AS
(
SELECT (1000*t1.num) + (100*t2.num) + (10*t3.num) + t4.num-5000 as gen_num
FROM ten_numbers AS t1
JOIN ten_numbers AS t2 ON 1 = 1
JOIN ten_numbers AS t3 ON 1 = 1
JOIN ten_numbers AS t4 ON 1 = 1
)
select gen_num from generted_numbers
where gen_num between -10 and 0
order by 1;
I have a requirement to create a table with an identifier column. The identifier data will be comprised of 3 parts, the first being a letter [A-Z], the second being a number [1-42] and the third being again a number [1-6].
I was wondering the quickest and best way to go about this as I'm really stuck. The output should look like this:
A-1-1
A-1-2
A-1-3
...
Z-42-6
Thanks for your help
You should use CROSS JOIN with derived tables containing all letters/numbers needed
SELECT letters.let + '-' + numbers.num + '-' + numbers2.num
FROM(SELECT 'A' as let UNION ALL SELECT 'B' .....) letters
CROSS JOIN(SELECT '1' as num UNION ALL SELECT '2' ....) numbers -- up to 42
CROSS JOIN(SELECT '1' as num UNION ALL SELECT '2' ....) numbers2 -- up to 6
Here is a cut-down version using CROSS JOIN acrross 3 valued tables
SELECT v1.val + '-' + CAST(v2.val AS VARCHAR(5)) + '-' + cast(v3.val AS VARCHAR(5))
FROM
(VALUES ('A'),('B'),('C'),('D')) v1(val)
CROSS JOIN
(VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12),(13),(14),(15),(16)) v2(val)
CROSS JOIN
(VALUES (1),(2),(3),(4),(5),(6)) v3(val)
A Tally table would save you the need to write all the values one by one.
If you don't already have a tally table, read this post on the best way to create one.
SELECT Letter +'-'+ cast(fn as varchar(2)) +'-'+ cast(sn as char(1))
FROM (SELECT CHAR(Number) As Letter FROM Tally WHERE Number BETWEEN 65 AND 90) a
CROSS JOIN (SELECT Number as fn FROM Tally WHERE Number BETWEEN 1 AND 42) b
CROSS JOIN (SELECT Number as sn FROM Tally WHERE Number BETWEEN 1 AND 6) c
Just for fun, a mathematical approach:
with cte as
(
select 0 nr
union all
select nr+1 from cte where nr < 6551 --(26 * 42 * 6 = 6552 , 0 based = 6551)
)
select char(65 + (nr / 252)), 1 + ((nr / 6) % 42), 1 + nr % 6, * from cte -- Letter: divider = 6 * 42 = 252 , 65 = 'A'
option (maxrecursion 10000)
The cte only generated a stream of numbers from 0 to 6551 (could be done with other approaches as well).
After that each segment of the sequence can be calculated.
But for the record, once a sequence is created, I like Zohar's solution best :)
One more way:
;WITH cte AS (
SELECT 1 as digit
UNION ALL
SELECT digit + 1
FROM cte
WHERE digit < 90
)
SELECT CHAR(c1.digit) + '-' +
CAST(c2.digit as nvarchar(2)) + '-' +
CAST(c3.digit as nvarchar(2)) as seq
FROM cte c1
CROSS JOIN (SELECT digit FROM cte WHERE digit between 1 and 42) c2
CROSS JOIN (SELECT digit FROM cte WHERE digit between 1 and 6) c3
WHERE c1.digit between 65 and 90 --65..90 in ASCII is A..Z
Output:
seq
A-1-1
A-1-2
A-1-3
A-1-4
A-1-5
A-1-6
A-2-1
A-2-2
A-2-3
A-2-4
A-2-5
A-2-6
...
Z-42-3
Z-42-4
Z-42-5
Z-42-6
This is my query.
SELECT TOP 2 NUM
FROM QT_PIVOT
WHERE NUM BETWEEN 1 AND 45
ORDER BY NEWID()
I'm selecting 2 random numbers from a list but I don't want that these numbers to be continuous
Sometimes the result is
NUM
----
2
3
And I don't want this
Thanks , and sorry for my English u.u
Basically the same as the 2nd approach Gordon uses except it lacks the use of the lag function and therefor will work on SQL-2008.
WITH Data AS(
SELECT *, RowNum = ROW_NUMBER() OVER (ORDER BY NEWID())
FROM sys.objects AS O
),
r AS(
SELECT TOP 1 *, SkipRow = 0
FROM Data
WHERE Data.RowNum = 1
UNION ALL
SELECT d.*, SkipRow = CASE WHEN d.object_id BETWEEN r.object_id -2 AND r.object_id + 2 THEN 1 ELSE 0 END
FROM r
JOIN Data AS D
ON r.RowNum + 1 = D.RowNum
)
SELECT TOP 2 * FROM R
WHERE R.SkipRow = 0
One approach is to select the first number, and then select an appropriate second number:
WITH r AS (
SELECT TOP 1 num
FROM QT_PIVOT
WHERE NUM BETWEEN 1 AND 45
ORDER BY NEWId()
)
select num
from r
union all
select top 1 q.num
from qt_pivot q join
r
on q.num not in (r.num, r.num - 1, r.num + 1)
where q.num between 1 and 45
order by newid();
Another approach (if you had SQL Server 2012+) would use lag() to remove any possibilities that do not meet the conditions:
WITH r AS (
SELECT num, row_number() over (order by newid()) as seqnum
FROM QT_PIVOT
WHERE NUM BETWEEN 1 AND 45
)
SELECT r.num
FROM (SELECT r.*, LAG(num) OVER (ORDER BY seqnum) as prevnum
FROM r
) r
WHERE prevnum is null or
prevnum not in (num - 1, num + 1);
EDIT:
The first approach doesn't work, because SQL Server always re-evaluates CTEs, and there is not even a hint to fix this problem. Here is an alternative approach, that will ensure that values are not consecutive:
WITH r as (
SELECT (1 + checksum(newid()) * 45) as r1,
(2 + checksum(newid()) * 43) as r2
)
SELECT q.num
FROM QT_PIVOT q
WHERE q.num = r.r1 or
q.num = 1 + (r.r1 + r.r2) % 45;
This calculates a two random numbers. The first is a random position. The second is an allowable offset (hence the "2" and "43") to guarantee that the numbers are not adjacent.
Is there an elegant way in SQL Server to find all the distinct characters in a single varchar(50) column, across all rows?
Bonus points if it can be done without cursors :)
For example, say my data contains 3 rows:
productname
-----------
product1
widget2
nicknack3
The distinct inventory of characters would be "productwigenka123"
Here's a query that returns each character as a separate row, along with the number of occurrences. Assuming your table is called 'Products'
WITH ProductChars(aChar, remain) AS (
SELECT LEFT(productName,1), RIGHT(productName, LEN(productName)-1)
FROM Products WHERE LEN(productName)>0
UNION ALL
SELECT LEFT(remain,1), RIGHT(remain, LEN(remain)-1) FROM ProductChars
WHERE LEN(remain)>0
)
SELECT aChar, COUNT(*) FROM ProductChars
GROUP BY aChar
To combine them all to a single row, (as stated in the question), change the final SELECT to
SELECT aChar AS [text()] FROM
(SELECT DISTINCT aChar FROM ProductChars) base
FOR XML PATH('')
The above uses a nice hack I found here, which emulates the GROUP_CONCAT from MySQL.
The first level of recursion is unrolled so that the query doesn't return empty strings in the output.
Use this (shall work on any CTE-capable RDBMS):
select x.v into prod from (values('product1'),('widget2'),('nicknack3')) as x(v);
Test Query:
with a as
(
select v, '' as x, 0 as n from prod
union all
select v, substring(v,n+1,1) as x, n+1 as n from a where n < len(v)
)
select v, x, n from a -- where n > 0
order by v, n
option (maxrecursion 0)
Final Query:
with a as
(
select v, '' as x, 0 as n from prod
union all
select v, substring(v,n+1,1) as x, n+1 as n from a where n < len(v)
)
select distinct x from a where n > 0
order by x
option (maxrecursion 0)
Oracle version:
with a(v,x,n) as
(
select v, '' as x, 0 as n from prod
union all
select v, substr(v,n+1,1) as x, n+1 as n from a where n < length(v)
)
select distinct x from a where n > 0
Given that your column is varchar, it means it can only store characters from codes 0 to 255, on whatever code page you have. If you only use the 32-128 ASCII code range, then you can simply see if you have any of the characters 32-128, one by one. The following query does that, looking in sys.objects.name:
with cteDigits as (
select 0 as Number
union all select 1 as Number
union all select 2 as Number
union all select 3 as Number
union all select 4 as Number
union all select 5 as Number
union all select 6 as Number
union all select 7 as Number
union all select 8 as Number
union all select 9 as Number)
, cteNumbers as (
select U.Number + T.Number*10 + H.Number*100 as Number
from cteDigits U
cross join cteDigits T
cross join cteDigits H)
, cteChars as (
select CHAR(Number) as Char
from cteNumbers
where Number between 32 and 128)
select cteChars.Char as [*]
from cteChars
cross apply (
select top(1) *
from sys.objects
where CHARINDEX(cteChars.Char, name, 0) > 0) as o
for xml path('');
If you have a Numbers or Tally table which contains a sequential list of integers you can do something like:
Select Distinct '' + Substring(Products.ProductName, N.Value, 1)
From dbo.Numbers As N
Cross Join dbo.Products
Where N.Value <= Len(Products.ProductName)
For Xml Path('')
If you are using SQL Server 2005 and beyond, you can generate your Numbers table on the fly using a CTE:
With Numbers As
(
Select Row_Number() Over ( Order By c1.object_id ) As Value
From sys.columns As c1
Cross Join sys.columns As c2
)
Select Distinct '' + Substring(Products.ProductName, N.Value, 1)
From Numbers As N
Cross Join dbo.Products
Where N.Value <= Len(Products.ProductName)
For Xml Path('')
Building on mdma's answer, this version gives you a single string, but decodes some of the changes that FOR XML will make, like & -> &.
WITH ProductChars(aChar, remain) AS (
SELECT LEFT(productName,1), RIGHT(productName, LEN(productName)-1)
FROM Products WHERE LEN(productName)>0
UNION ALL
SELECT LEFT(remain,1), RIGHT(remain, LEN(remain)-1) FROM ProductChars
WHERE LEN(remain)>0
)
SELECT STUFF((
SELECT N'' + aChar AS [text()]
FROM (SELECT DISTINCT aChar FROM Chars) base
ORDER BY aChar
FOR XML PATH, TYPE).value(N'.[1]', N'nvarchar(max)'),1, 1, N'')
-- Allow for a lot of recursion. Set to 0 for infinite recursion
OPTION (MAXRECURSION 365)
WITH y AS (
WITH x AS (
SELECT * FROM MyTable
)
SELECT * FROM x
)
SELECT * FROM y
Does something like this work? I tried it earlier but I couldn't get it to work.
While not strictly nested, you can use common table expressions to reuse previous queries in subsequent ones.
To do this, the form of the statement you are looking for would be
WITH x AS
(
SELECT * FROM MyTable
),
y AS
(
SELECT * FROM x
)
SELECT * FROM y
You can do the following, which is referred to as a recursive query:
WITH y
AS
(
SELECT x, y, z
FROM MyTable
WHERE [base_condition]
UNION ALL
SELECT x, y, z
FROM MyTable M
INNER JOIN y ON M.[some_other_condition] = y.[some_other_condition]
)
SELECT *
FROM y
You may not need this functionality. I've done the following just to organize my queries better:
WITH y
AS
(
SELECT *
FROM MyTable
WHERE [base_condition]
),
x
AS
(
SELECT *
FROM y
WHERE [something_else]
)
SELECT *
FROM x
With does not work embedded, but it does work consecutive
;WITH A AS(
...
),
B AS(
...
)
SELECT *
FROM A
UNION ALL
SELECT *
FROM B
EDIT
Fixed the syntax...
Also, have a look at the following example
SQLFiddle DEMO
These answers are pretty good, but as far as getting the items to order properly, you'd be better off looking at this article
http://dataeducation.com/dr-output-or-how-i-learned-to-stop-worrying-and-love-the-merge
Here's an example of his query.
WITH paths AS (
SELECT
EmployeeID,
CONVERT(VARCHAR(900), CONCAT('.', EmployeeID, '.')) AS FullPath
FROM EmployeeHierarchyWide
WHERE ManagerID IS NULL
UNION ALL
SELECT
ehw.EmployeeID,
CONVERT(VARCHAR(900), CONCAT(p.FullPath, ehw.EmployeeID, '.')) AS FullPath
FROM paths AS p
JOIN EmployeeHierarchyWide AS ehw ON ehw.ManagerID = p.EmployeeID
)
SELECT * FROM paths order by FullPath
we can create nested cte.please see the below cte in example
;with cte_data as
(
Select * from [HumanResources].[Department]
),cte_data1 as
(
Select * from [HumanResources].[Department]
)
select * from cte_data,cte_data1
I was trying to measure the time between events with the exception of what one entry that has multiple processes between the start and end. I needed this in the context of other single line processes.
I used a select with an inner join as my select statement within the Nth cte. The second cte I needed to extract the start date on X and end date on Y and used 1 as an id value to left join to put them on a single line.
Works for me, hope this helps.
cte_extract
as
(
select ps.Process as ProcessEvent
, ps.ProcessStartDate
, ps.ProcessEndDate
-- select strt.*
from dbo.tbl_some_table ps
inner join (select max(ProcessStatusId) ProcessStatusId
from dbo.tbl_some_table
where Process = 'some_extract_tbl'
and convert(varchar(10), ProcessStartDate, 112) < '29991231'
) strt on strt.ProcessStatusId = ps.ProcessStatusID
),
cte_rls
as
(
select 'Sample' as ProcessEvent,
x.ProcessStartDate, y.ProcessEndDate from (
select 1 as Id, ps.Process as ProcessEvent
, ps.ProcessStartDate
, ps.ProcessEndDate
-- select strt.*
from dbo.tbl_some_table ps
inner join (select max(ProcessStatusId) ProcessStatusId
from dbo.tbl_some_table
where Process = 'XX Prcss'
and convert(varchar(10), ProcessStartDate, 112) < '29991231'
) strt on strt.ProcessStatusId = ps.ProcessStatusID
) x
left join (
select 1 as Id, ps.Process as ProcessEvent
, ps.ProcessStartDate
, ps.ProcessEndDate
-- select strt.*
from dbo.tbl_some_table ps
inner join (select max(ProcessStatusId) ProcessStatusId
from dbo.tbl_some_table
where Process = 'YY Prcss Cmpltd'
and convert(varchar(10), ProcessEndDate, 112) < '29991231'
) enddt on enddt.ProcessStatusId = ps.ProcessStatusID
) y on y.Id = x.Id
),
.... other ctes
Nested 'With' is not supported, but you can always use the second With as a subquery, for example:
WITH A AS (
--WITH B AS ( SELECT COUNT(1) AS _CT FROM C ) SELECT CASE _CT WHEN 1 THEN 1 ELSE 0 END FROM B --doesn't work
SELECT CASE WHEN count = 1 THEN 1 ELSE 0 END AS CT FROM (SELECT COUNT(1) AS count FROM dual)
union all
select 100 AS CT from dual
)
select CT FROM A