I have two tables - tool_downloads and tool_configurations. I am trying to retrieve the most recent build date for each tool in my database. The layout of the DB is simple. One table called tool_downloads keeps track of when a tool is downloaded. Another table is called tool_configurations and stores the actual data about the tool. They are linked together by the tool_conf_id.
If I run the following query which omits dates, I get back 200 records.
SELECT DISTINCT a.tool_conf_id, b.tool_conf_id
FROM tool_downloads a
JOIN tool_configurations b
ON a.tool_conf_id = b.tool_conf_id
ORDER BY a.tool_conf_id
When I try to add in date information I get back hundreds of thousands of records! Here is the query that fails horribly.
SELECT DISTINCT a.tool_conf_id, max(a.configured_date) as config_date, b.configuration_name
FROM tool_downloads a
JOIN tool_configurations b
ON a.tool_conf_id = b.tool_conf_id
ORDER BY a.tool_conf_id
I know the problem has something to do with group-bys/aggregate data and joins. I can't really search google since I don't know the name of the problem I'm encountering. Any help would be appreciated.
Solution is:
SELECT b.tool_conf_id, b.configuration_name, max(a.configured_date) as config_date
FROM tool_downloads a
JOIN tool_configurations b
ON a.tool_conf_id = b.tool_conf_id
GROUP BY b.tool_conf_id, b.configuration_name
Related
I'm trying to read data from related tables which are x levels deep and which have relationships specified, i.e.:
table A
table B
table C
table ABC
Table ABC has relationships ABC.a = A, ABC.b = B and ABC.c = C,
i.e. foreign keys ABC.aid = A.id, ABC.bid = B.id and ABC.cid = C.id.
aid, bid and cid in ABC are set unique using UniqueContstraint
relationship is using lazy="joined"
When I do select(ABC) I'm able to get all values from ABC and also from related tables, i.e.:
{ABC.a: {A}, ABC.b: {B}, ABC.c: {C}}
I have also table D which has a relationship to ABC (D.abcid = ABC.id) and I struggle to construct a correct select statement which would give me all data also from A, B and C. Actually I'm not sure if this should work or I missed / do not understand something in the documentation as I have tried various loading strategies, specified join_depth for D and ABC tables, etc. No matter what I'm getting:
sqlalchemy.exc.InvalidRequestError: The unique() method must be invoked on this Result, as it contains results that include joined eager loads against collections
I would like to get the data the same way as for 1st level relationship, i.e.:
{D.abc : {ABC.a: {A}, ABC.b: {B}, ABC.c: {C}}}
Is it possible or do I have to change the select query completely and just create multiple joins and manually pick all the values I need?
I'm able to get correct records from the database when I just take the generated select statement and use it directly in a DB shell (MariaDB) so I assume that the only issue is my lack of understanding of how SQL handles/presents these records internally.
The issue was using uselist=True in one of the models, all relationships are working perfectly down to the lowest level now.
I don't get an except join to work in Cognos-11. Where or what am I missing?
Some understanding for a beginner in this branch would be nice ;-)
What I've tried so far is making two queries. The first one holds data items like "customer", "BeginningDate" and "Purpose". The second query holds data items like "customer", "Adress" and "Community".
What I'd like to accomplish is to get in query3: the "customers" from query1 that are not available in query2. To me it sounds like an except-join.
I went to the query work area, created a query3 and dragged an "except-join" icon on it. Then I dragged query1 into the upper space and query2 into the lower. What I'm used to getting with other joins, is a possibility to set a new link, cardinality and so on. Now double clicking the join isn't opening any pop-up. The properties of the except-join show "Set operation = Except", "Duplicates = remove", "Projection list = Manual".
How do I get query3 filled with the data item "customer" that only holds a list of customers which are solely appearing in query1?
In SQL terms, you want
select T2.C1
from T1
left outer join T2 on T1.C1 = T2.C1
where T2.C1 is null
So, in the query pane of a Cognos report...
Use a regular join.
Join using customer from both queries.
Change the cardinality to 1..1 on the query1 side and 0..1 on the query2 side.
In the filters for query3, add a filter for query2.customer is null.
EXCEPT is not a join. It is used to compare two data sets.
https://learn.microsoft.com/en-us/sql/t-sql/language-elements/set-operators-except-and-intersect-transact-sql?view=sql-server-2017
What you need is an INNER JOIN. That would be the join tool in the Toolbox in Cognos.
Say you creating an imdb type site for TV Shows. You have a Show with many attached episodes and a bunch of people
Right now I link people to episodes though a contribution table - but if I want to make a list of all the shows they are on, I have to go through episodes.
Since this query takes a long time I was thinking about adding show_id to the contributions table. Is this common practice to increase performance or is there another way I haven't thought of?
Since this query takes a long time
Have you run a SQL explain plan to show why this is the case? What is the actual SQL query that is being run, and are you doing things like ordering or running subqueries within it?
If I understand your structure it is something like this:
|people| n---1 |contribution| 1---n |episodes| n---1 |shows|
A sql select of the sort:
select distinct s.name
from shows s,
episodes e,
contribution c
where c.people_id = <id>
and c.episode_id = e.id
and e.show_id = s.id
should really not have performance issues unless there are no indexes on the tables or the tables are massive.
Here's a way using where id in ( ... ) to select all shows a specific person appeared in
Shows.where(id: Contribution.select("show_id")
.join(:episodes)
.where(person_id: personId)
.group("episodes.show_id"))
You may also want to try exists
Shows.where("EXISTS(SELECT 1 from contributions c
join episodes e on e.id = c.episode_id
where c.person_id = ? and e.show_id = shows.id)")
I have a SQL query something like this
SELECT
P . ID,
P .code,
l.parent_id
FROM
properties P
LEFT JOIN locations l ON l. ID = P .location_id;
I want to convert this query to SOLR query. I can join two cores by below system
http://example.com:8999/solr/properties/select?q=*:*&fq={!join from=id to=location_id fromIndex=locations}p_id:12345
But I cant select the fields of locations core.How can I do this? Your valuable suggestion will be appreciated.
You can use subquery in the fl. Something like this fl=*,locations:[subquery fromIndex=locations]&locations.q={!terms f=id v=$row.location_id}
More info here https://lucene.apache.org/solr/guide/6_6/transforming-result-documents.html#TransformingResultDocuments-subquery
You can't. Solr does not support returning fields from both ends of an join. Solr is not a relational database, so you're usually better off trying to not use it as one.
Instead, index the information about each location to each property, and query based on that.
If any location info changes (which it turns out, usually happens very rarely), reindex the documents assigned that location.
I have a sqlite database that I'm trying to build a query. The table column I need to retrieve is iEDLID from the table below :
Right now all I have to go on is a known iEventID from the table below :
And the the nClientLocationID from the table below.
So the requirements are I need to get current iEDLID to write, lookup from tblEventDateLocations for dEventDate and the tblLocation.nClientLocationID based on the tblLocations.iLocationID I already have and event selected on this screen.
So I would need a query that does a "SELECT DISTINCT table EventDateLocations.iEDLID FROM tblEventDateLocations ...."
So basically from another query I have the iEventID I need, and I have the event ID i need but where the dEventDate=(select date('now')) I need to retrieve the iEventDateID from table EventDates.iEventDateID to use on the table EventDateLocations
this is the point where I'm trying to wrap my head around the joins for this query and the syntax...
It seems like you want this:
select distinct edl.iEDLDID
from
tblEventDateLocations edl
join tblEventDates ed on edl.EventDateId = ed.EventDateId
where
ed.EventId = ?
and ed.dEventDate = date('now')
and edl.nClientLocationID = ?
where the ? of course represent the known event ID and location ID parameters.
Since nClientLocationId appears on table tblEventDateLocations you do not need to join table tblLocations unless you want to filter out results whose location ID does not appear in that table.