I have a query I need to run that returns the most recently updated row for each client.
In SQL Server, I would do the following:
SELECT *
FROM
(
SELECT *, ROW_NUMBER() OVER (PARTITION BY client_id ORDER BY date_updated DESC) AS rn
FROM client_address
) a
WHERE a.rn = 1
Is there a similar way to do this on Intersystems Cache? I'm not finding any documentation for any type of ranking function.
I looked at the docs and the doesn't appear to be any of the Window functions that exist in SQL Server, Oracle or Postgres so you're stuck with the ANTI-THETA-SELF-JOIN solution.
SELECT *
FROM
client_address a
LEFT JOIN client_address b
on a.client_id = b.client_id
and a.date_updated < b.date_updated
WHERE
b.client_id is null
See the documentation for HAVING. Here's how to use it in this case:
SELECT *
FROM client_address
GROUP BY client_id
HAVING date_updated = MIN(date_updated)
You can use %vid variable. For example:
SELECT *, %vid FROM (SELECT * FROM Sample.Person) WHERE %vid BETWEEN 5 AND 10
would return rows 5-10 from Sample.Person table.
Documentation.
Discussion on InterSystems Caché developer community.
SELECT *
FROM client_address a
WHERE
a.date_updated = (
SELECT max(b.date_updated) FROM client_address b
group by b.Client_id
)
Related
Hi I have a query which looks like the following :
SELECT device_id, tag_id, at, _deleted, data,
row_number() OVER (PARTITION BY device_id ORDER BY at DESC) AS row_num
FROM mdb_history.devices_tags_mapping_history
WHERE at <= '2019-04-01'
AND _deleted = False
AND (tag_id = '275674' or tag_id = '275673')
AND row_num = 1
However when I run the following query, I get the following error :
ERROR: column "row_num" does not exist
Is there any way to go about this. One way I tried was to use it in the following way:
SELECT * from (SELECT device_id, tag_id, at, _deleted, data,
row_number() OVER (PARTITION BY device_id ORDER BY at DESC) AS row_num
FROM mdb_history.devices_tags_mapping_history
WHERE at <= '2019-04-01'
AND _deleted = False
AND (tag_id = '275674' or tag_id = '275673')) tag_deleted
WHERE tag_deleted.row_num = 1
But this becomes way too complicated as I do it with other queries as I have number of join and I have to select the column as stated from so it causes alot of select statement. Any smart way of doing that in a more simpler way. Thanks
You can't refer to the row_num alias which you defined in the same level of the select in your query. So, your main option here would be to subquery, where row_num would be available. But, Postgres actually has an option to get what you want in another way. You could use DISTINCT ON here:
SELECT DISTINCT ON (device_id), device_id, tag_id, at, _deleted, data
FROM mdb_history.devices_tags_mapping_history
WHERE
at <= '2019-04-01' AND
_deleted = false AND
tag_id IN ('275674', '275673')
ORDER BY
device_id,
at DESC;
Too long/ formatted for a comment. There is a reason behind #TimBiegeleisen statement "alias which you defined in the same level of the select". That reason is that all SQL statement follow the same sequence for evaluation. Unfortunately that sequence does NOT follow the sequence of clauses within the statement presentation. that sequence is in order:
from
where
group by
having
select
limits
You will notice that what actually gets selected fall well after evaluation of the where clause. Since your alias is defined within the select phase it does not exist during the where phase.
I'm having trouble with paginating with joined tables in DB2. I want to return rows 10-30 of a query that contains an INNER JOIN.
This works:
SELECT *
FROM (
SELECT row_number() OVER (ORDER BY U4SLSMN.SLNAME) AS ID,
U4SLSMN.SLNO, U4SLSMN.SLNAME, U4SLSMN.SLLC
FROM U4SLSMN) AS P
WHERE P.ID BETWEEN 10 AND 30
This does not work:
SELECT *
FROM (
SELECT row_number() OVER (ORDER BY U4SLSMN.SLNAME) AS ID,
U4SLSMN.SLNO, U4SLSMN.SLNAME, U4SLSMN.SLLC, U4CONST.C4NAME
FROM U4SLSMN INNER JOIN U4CONST ON U4SLSMN.SLNO = U4CONST.C4NAME
) AS P
WHERE P.ID BETWEEN 10 AND 30
The error I get is:
Selection error involving field *N.
Note that the JOIN query works correctly by itself, just not when it's run as a subquery.
How do I perform a join inside a subquery in DB2?
Works fine for me on v7.1 TR9
Here's what I actually ran:
select *
from ( select rownumber() over (order by vvname) as ID, idescr, vvname
from olsdta.ioritemmst
inner join olsdta.vorvendmst on ivndno = vvndno
) as P
where p.id between 10 and 30;
I much prefer the CTE version however:
with p as
( select rownumber() over (order by vvname) as ID, idescr, vvname
from olsdta.ioritemmst
inner join olsdta.vorvendmst on ivndno = vvndno
)
select *
from p
where p.id between 10 and 30;
Finally, note that at 7.1 TR11 (7.2 TR3), IBM added support of the LIMIT and OFFSET clauses. Your query could be re-done as follows:
SELECT
U4SLSMN.SLNO, U4SLSMN.SLNAME, U4SLSMN.SLLC, U4CONST.C4NAME
FROM U4SLSMN INNER JOIN U4CONST ON U4SLSMN.SLNO = U4CONST.C4NAME
ORDER BY U4SLSMN.SLNAME
LIMIT 20 OFFSET 9;
However, note that the LIMIT & OFFSET clauses are only supported in prepared or embedded SQL. You can't use them in STRSQL or STRQMQRY. I believe the "Run SQL Scripts" GUI interface does support them. Here's an article about LIMIT & OFFSET
given a query like so:
SELECT
id,
(SELECT COUNT(*)
FROM members
WHERE members.network_id = networks.id) AS mem_count
FROM
networks
WHERE mem_count > 2
With this query, the where clause breaks as it does not know what mem_count is... Why can't I use the as var in the where clause?
Thanks
While bernie suggested correct answer to the question, your query can be simplified to:
SELECT
network_id as id,
count(*)
FROM
members
GROUP BY
network_id
HAVING
count(*) > 2
Which, as an additional bonus, can be faster.
You've got the concept down. You just need the right syntax. You could re-write like this and have the added benefit of making your query ANSI-compliant:
SELECT
id,
m.mem_count
FROM
networks n
JOIN (
SELECT m.network_id,
COUNT(*) AS mem_count
FROM members
GROUP BY m.network_id
) m
ON m.network_id = n.id
AND m.mem_count > 2;
Try:
SELECT
id,
(SELECT COUNT(*) as mem_count
FROM members
WHERE members.network_id = networks.id)
FROM
networks
WHERE mem_count > 2
One way would be.
Select * From (
SELECT
id,
(SELECT COUNT(*)
FROM members
WHERE members.network_id = networks.id) AS mem_count
FROM
networks)) mem_counts
WHERE mem_count > 2
A join as suggested by Bernie would be better though. Basically you confused the parser. You get the same sort of issue with group by or order by when you use AS to alias a column name.
I have the following table
-----Account#----Period-----Balance
12345---------200901-----$11554
12345---------200902-----$4353
12345 --------201004-----$34
12345 --------201005-----$44
12345---------201006-----$1454
45677---------200901-----$14454
45677---------200902-----$1478
45677 --------201004-----$116776
45677 --------201005-----$996
56789---------201006-----$1567
56789---------200901-----$7894
56789---------200902-----$123
56789 --------201003-----$543345
56789 --------201005-----$114
56789---------201006-----$54
I want to select the account# that have a period of 201005.
This is fairly easy using the code below. The problem is that if a user enters 201003-which doesnt exist- I want the query to select the previous value.*NOTE that there is an account# that has a 201003 period and I still want to select it too.*
I tried CASE, IF ELSE, IN but I was unsuccessfull.
PS:I cannot create temp tables due to system limitations of 5000 rows.
Thank you.
DECLARE #INPUTPERIOD INT
#INPUTPERIOD ='201005'
SELECT ACCOUNT#, PERIOD , BALANCE
FROM TABLE1
WHERE PERIOD =#INPUTPERIOD
SELECT t.ACCOUNT#, t.PERIOD, t.BALANCE
FROM (SELECT ACCOUNT#, MAX(PERIOD) AS MaxPeriod
FROM TABLE1
WHERE PERIOD <= #INPUTPERIOD
GROUP BY ACCOUNT#) q
INNER JOIN TABLE1 t
ON q.ACCOUNT# = t.ACCOUNT#
AND q.MaxPeriod = t.PERIOD
select top 1 account#, period, balance
from table1
where period >= #inputperiod
; WITH Base AS
(
SELECT *, ROW_NUMBER() OVER (ORDER BY Period DESC) RN FROM #MyTable WHERE Period <= 201003
)
SELECT * FROM Base WHERE RN = 1
Using CTE and ROW_NUMBER() (we take all the rows with Period <= the selected date and we take the top one (the one with auto-generated ROW_NUMBER() = 1)
; WITH Base AS
(
SELECT *, 1 AS RN FROM #MyTable WHERE Period = 201003
)
, Alternative AS
(
SELECT *, ROW_NUMBER() OVER (ORDER BY Period DESC) RN FROM #MyTable WHERE NOT EXISTS(SELECT 1 FROM Base) AND Period < 201003
)
, Final AS
(
SELECT * FROM Base
UNION ALL
SELECT * FROM Alternative WHERE RN = 1
)
SELECT * FROM Final
This one is a lot more complex but does nearly the same thing. It is more "imperative like". It first tries to find a row with the exact Period, and if it doesn't exists does the same thing as before. At the end it unite the two result sets (one of the two is always empty). I would always use the first one, unless profiling showed me the SQL wasn't able to comprehend what I'm trying to do. Then I would try the second one.
I need to select from a CTE (common table expression) in DB2 v8 and insert the result into a table.
The relevant documentation for v8 is hard to understand at first glance, but for v9 there's a clear example (http://publib.boulder.ibm.com/infocenter/dzichelp/v2r2/index.jsp?topic=/com.ibm.db29.doc.apsg/db2z_createcte.htm):
INSERT INTO vital_mgr (mgrno)
WITH VITALDEPT (deptno, se_count) AS
(
SELECT deptno, count(*)
FROM DSN8910.EMP
WHERE job = 'senior engineer'
GROUP BY deptno
)
SELECT d.manager
FROM DSN8910.DEPT d
, VITALDEPT s
WHERE d.deptno = s.deptno
AND s.se_count > (
SELECT AVG(se_count)
FROM VITALDEPT
);
It does not work in v8 though.
How should it be written in v8?
Write it like a boss
INSERT INTO vital_mgr
(
SELECT d.manager
FROM SN8910.DEPT AS d
INNER JOIN
(
SELECT deptno, count(*)
FROM DSN8910.EMP
WHERE job = 'senior engineer'
GROUP BY deptno
) AS s (deptno, se_count)
ON d.deptno = s.deptno
WHERE s.se_count > (
SELECT AVG(se_count)
FROM
(
SELECT deptno, count(*)
FROM DSN8910.EMP
WHERE job = 'senior engineer'
GROUP BY deptno
) AS VITALDEPT (deptno, se_count)
)
);
There's a simple workaround here that allows you to use an INSERT or UPDATE using a conventional WITH statement. This hack will work for INSERT on V8 or greater, and for UPDATE on V9 or greater.
There are other methods for V8 or greater, typically using sub-selects, but I find them to be unpractical due to their complexity.