This query generates the numbers from 1 to 4.
with recursive z(q) as (
select 1
union all
select q + 1 from z where q < 4
)
select * from z;
But, if I modify it to this,
with x as (
select 1 y
),
recursive z(q) as (
select y from x
union all
select q + 1 from z where q < 4
)
select * from z;
It gives
ERROR: syntax error at or near "z"
What did i do wrong here?
I think this is because RECURSIVE is modifier of WITH statement, not a property of common table expression z, so you can use it like this:
with recursive
x as (
select 1 y
),
z(q) as (
select y from x
union all
select q + 1 from z where q < 4
)
select * from z;
sql fiddle demo
Related
I tried to create a simple SQL to track query_history usage, but got into trouble when creating my timeslots using the table and generator functions (the CTE named x below).
I got no results at all when limiting the query_history using my timeslots, so after a while I hardcoded an SQL to give the same result (the CTE named y below) and this works fine.
Why does not x work? As far as I can see x and y produce identical result?
To test the example first run the code as it is, this produces no result.
Then comment the line x as timeslots and un-comment the line y as timeslots, this will give the desired result.
with
x as (
select
dateadd('min',seq4()*10,dateadd('min',-60,current_timestamp())) f,
dateadd('min',(seq4()+1)*10,dateadd('min',-60,current_timestamp())) t
from table(generator(rowcount => 6))
),
y as (
select
dateadd('min',n*10,dateadd('min',-60,current_timestamp())) f,
dateadd('min',(n+1)*10,dateadd('min',-60,current_timestamp())) t
from (select 0 n union all select 1 n union all select 2 union all select 3
union all select 4 union all select 5)
)
--select * from x;
--select * from y;
select distinct
user_name,
timeslots.f
from snowflake.account_usage.query_history,
x as timeslots
--y as timeslots
where start_time >= timeslots.f
and start_time < timeslots.t
order by timeslots.f desc;
(I know the code is not optimal, this is only meant to illustrate the problem)
SEQ:
Returns a sequence of monotonically increasing integers, with wrap-around. Wrap-around occurs after the largest representable integer of the integer width (1, 2, 4, or 8 byte).
If a fully ordered, gap-free sequence is required, consider using the ROW_NUMBER window function.
For:
with x as (
select
dateadd('min',seq4()*10,dateadd('min',-60,current_timestamp())) f,
dateadd('min',(seq4()+1)*10,dateadd('min',-60,current_timestamp())) t
from table(generator(rowcount => 6))
)
SELECT * FROM x;
Should be:
with x as (
select
(ROW_NUMBER() OVER(ORDER BY seq4())) - 1 AS n,
dateadd('min',n*10,dateadd('min',-60,current_timestamp())) f,
dateadd('min',(n+1)*10,dateadd('min',-60,current_timestamp())) t
from table(generator(rowcount => 6))
)
SELECT * FROM x;
Let's consider the following query:
with
init as (
select 0.1 as y0
),
cte as (
select 1 as i, 1 as x -- x_1
union all
select 2 as i, 10 as x -- x_2
union all
select 3 as i, 100 as x -- x_3
order by i asc
)
select cte.x, init.y0 -- <- ?
from cte
join init
on true
There is a CTE init specifying an inital value y_0 and a CTE cte specifying rows with a value x and an index i.
My question is whether I can write a select which realizes the following simple, recursive formula.
y_n+1 = y_n + x_n+1
So, the result should be 3 rows with values: 1.1, 11.1, 111.1 (for y_1, y_2, y_3).
Would that be possible?
write a select which realizes the following simple, recursive formula.
y_n+1 = y_n + x_n+1
Consider below
select x, y0 + sum(x) over(order by i) as y
from cte, init
if applied to sample data in your question - output is
Note: the expected result you shown in your question - does not match the formula you provided - so obviously above output is different from one in your question :o)
You need to use the “OVER” statement. You can see more documentation about the syntax.
with
init as (
select 0.1 as y0
),
cte as (
select 1 as ts, 1 as i, 1 as x -- x_1
union all
select 2, 2, 10 as x -- x_2
union all
select 3, 3, 100 as x
union all
select 4, 4, 109 as x -- x_3
union all
select 5, 5, 149 as x
order by i asc
)
SELECT *,init.y0 + SUM(i) OVER(
ORDER BY (ts)
) AS res
FROM cte join init
on true
I have something like the following scenario
Select x, y, z
from mytable
where x = 1
UNION
Select x, y, z
from mytable2
where x = 1
I would like to put the results into a #TempTable and then create a Pivot of the results into #TempTable2
I have tried
SELECT * INTO #TempTable FROM (
Select x, y, z
from mytable
where x = 1
UNION
Select x, y, z
from mytable2
where x = 1
)
But it get Incorrect syntax near ')'
I've forgotten all the other variations I have made but none of them have worked
Add an alias to the derived table. Here I use X because I'm imaginative
SELECT *
INTO #TempTable
FROM
(
Select x, y, z
from mytable
where x = 1
UNION
Select x, y, z
from mytable2
where x = 1
) AS X
SQL Server needs a reference for the objects in the FROM clause. No alias = no reference
You can see this if we rewrite the query using a CTE
WITH myUnion AS
(
Select x, y, z
from mytable
where x = 1
UNION
Select x, y, z
from mytable2
where x = 1
)
SELECT *
INTO #TempTable
FROM myUnion
This query works:
SELECT
TOP 100 SUBSTRING(column_name FROM 6 FOR CHARACTER_LENGTH(column_name) - 5) AS X
FROM db_name.table_name
But the following query (with WHERE clause added) does not execute.
SELECT
TOP 100 SUBSTRING(column_name FROM 6 FOR CHARACTER_LENGTH(column_name) - 5) AS X
FROM db_name.table_name
WHERE NOT EXISTS
(
SELECT 1
FROM db_name2.lookup_name H
WHERE H.SRC_NUM1 = X
AND H.SRC_TYPE = 11
)
The query above throws
SELECT Failed. 2663: SUBSTR: string subscript out of bounds in table_name.column_name
However, this following one works (original SELECT is nested)
SELECT *
FROM (
SELECT
TOP 100 SUBSTRING(column_name FROM 6 FOR CHARACTER_LENGTH(column_name) - 5) AS X
FROM db_name.table_name
) A
WHERE NOT EXISTS
(
SELECT 1
FROM db_name2.lookup_name H
WHERE H.SRC_NUM1 = X
AND H.SRC_TYPE = 11
)
Why is that so? I am using SQL assistant to execute the queries but I doubt it is of relevance.
Try to change (maybe error is caused when column_name's lenght is less then 6):
SELECT
TOP 100 CASE WHEN CHARACTER_LENGTH(column_name)>5
THEN SUBSTRING(column_name FROM 6 FOR CHARACTER_LENGTH(column_name) - 5)
ELSE NULL END AS X
FROM db_name.table_name
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