Working in SQL Server 2008 where I only have access to create queries, not tables or views. My question is related to structuring code better.
I have views provided that give me multiple data sets with too much information. I'm attempting to slim the data down for easier use and reference, with requested specifics.
My goal is to have (3) main queries that list all of the data that I need, and to reference and reuse the data for multiple reports.
Query 1 - Incidents: lists all of the detail on a call
Query 2 - Units: lists all of the detail on units responding to a call
Query 3 - 1stUnits: lists all of the detail on 1st responding units only.
Because each of these queries will have multiple CASE statements within them, I was looking for a way to name the actual query, and reference the query in SQL as Qry1Calls or Qry2Units without an extensive subquery, within a query.
I've searched a bit, and found nothing.
It would be a lot easier to select Qry1 and Qry3 where id's match and filter those results by parameters.
Is this possible? I'm transitioning from Access with some SQL to full fledge SQL.
What you are looking for is probably Common Table Expressions (CTEs)
Read about them here:
https://msdn.microsoft.com/en-us/library/ms190766(SQL.90).aspx
Reference for the with keyword and examples here:
https://learn.microsoft.com/en-us/sql/t-sql/queries/with-common-table-expression-transact-sql
Related
I'm using MiniProfiler to check what NPoco is doing with SQL Server but I've noticed it reports duplicate queries even when the SQL parameters have different values.
Eg: if I fetch a string from a database by ID, I might call:
SELECT * FROM PageContent WHERE ID=#ID
...twice on the same page, with two different IDs, but MiniProfiler reports this as a duplicate query even though the results will obviously be different each time.
Is there any way I can get MiniProfiler to consider the SQL parameter values so it doesn't think these queries are duplicated? I'm not sure if this problem is part of MiniProfiler or if it's a problem in how NPoco reports it's actions to MiniProfiler so I'll tag both.
I think that this is by design, and is in fact one of the reasons for the existence of the duplicate query detection.
If you are running that query twice on one page where the only difference is the param value, then you could also run it one time and include both param values in that query.
SELECT * FROM PageContent WHERE ID in (#ID1, #ID2)
So you are doing with two queries what you could do with one (you would have to of course filter on server side, but that is faster than two queries).
The duplicate query label is not for saying that you are running the absolute identical query more than once (though it would apply there as well). Rather it is highlighting an opportunity for optimizing your query approach and consolidating different queries into one (think about what an N+1 situation would look like).
If the default functionality doesn't meet your needs, you can always change it! The functionality that calculates duplicateTimings is located in UI/includes.js. You can provide your own version of this file that defines duplicates in a different way (perhaps by looking at parameter values in addition to the command text when detecting duplicates) by turning on CustomUITemplates inside MiniProfiler, and putting your own version of includes.js in there.
I'm working on a data conversion utility which can push data from one master database out to a number of different databases. The utility its self will have no knowledge of how data is kept in the destination (table structure), but I would like to provide writing a SQL statement to return data from the destination using a complex SQL query with multiple join statements. As long as the data is in a standardized format that the utility can recognize (field names) in an ADO query.
What I would like to do is then modify the live data in this ADO Query. However, since there are multiple join statements, I'm not sure if it's possible to do this. I know at least with BDE (I've never used BDE), it was very strict and you had to return all fields (*) and such. ADO I know is more flexible, but I don't know quite how flexible in this case.
Is it supposed to be possible to modify data in a TADOQuery in this manner, when the results include fields from different tables? And even if so, suppose I want to append a new record to the end (TADOQuery.Append). Would it append to two different tables?
The actual primary table I'm selecting from has a complimentary table which is joined by the same primary key field, one is a "Small" table (brief info) and the other is a "Detail" table (more info for each record in Small table). So, a typical statement would include something like this:
select ts.record_uid, ts.SomeField, td.SomeOtherField from table_small ts
join table_detail td on td.record_uid = ts.record_uid
There are also a number of other joins to records in other tables, but I'm not worried about appending to those ones. I'm only worried about appending to the "Small" and "Detail" tables - at the same time.
Is such a thing possible in an ADO Query? I'm willing to tweak and modify the SQL statement in any way necessary to make this possible. I have a bad feeling though that it's not possible.
Compatibility:
SQL Server 2000 through 2008 R2
Delphi XE2
Editing these Fields which have no influence on the joins is usually no problem.
Appending is ... you can limit the Append to one of the Tables by
procedure TForm.ADSBeforePost(DataSet: TDataSet);
begin
inherited;
TCustomADODataSet(DataSet).Properties['Unique Table'].Value := 'table_small';
end;
but without an Requery you won't get much further.
The better way will be setting Values by Procedure e.g. in BeforePost, Requery and Abort.
If your View would be persistent you would be able to use INSTEAD OF Triggers
Jerry,
I encountered the same problem on FireBird, and from experience I can tell you that it can be made(up to a small complexity) by using CachedUpdates . A very good resource is this one - http://podgoretsky.com/ftp/Docs/Delphi/D5/dg/11_cache.html. This article has the answers to all your questions.
I have abandoned the original idea of live ADO query updates, as it has become more complex than I can wrap my head around. The scope of the data push project has changed, and therefore this is no longer an issue for me, however still an interesting subject to know.
The new structure of the application consists of attaching multiple "Field Links" on various fields from the original set of data. Each of these links references the original field name and a SQL Statement which is to be executed when that field is being imported. Multiple field links can be on one single field, therefore can execute multiple statements, placing the value in various tables, etc. The end goal was an app which I can easily and repeatedly export a common dataset from an original source to any outside source with different data structures, without having to recompile the app.
However the concept of cached updates was not appealing to me, simply for the fact pointed out in the link in RBA's answer that data can be changed in the database in the mean-time. So I will instead integrate my own method of customizable data pushes.
I have a table with about 30 fields. I current have several stored procedures which access either a (aggregated) view of this table or the table itself. For many of these SPs I would like to assure that the returned records have all the same fields with the same column names. Is there a way to do this where I don't have to change 20 stored procs if I do need to change the output.
My way around it thus far is to provide clients with lists of ID which they then call SP's that return the data however this seems to be slow compared with getting the data in one shot. I have also considered using the formatting stored procs with a cursor from inside the search stored procs but was unsure if that would really buy me a whole lot.
The typical way to define a standardised and consistent data access method across multiple stored procedures in SQL Server to use Views.
Now your problem description seems to suggest that you are already using Views in order to manage your data access. If you are indeed unable to use Views for a specific reason, perhaps you can clarify the nature of your problem further for us.
So I'm not necessarily saying this is even a good idea if it were possible, since the schema of the view would be extremely volatile, but is there any way to represent a has-many relationship in a single view?
For example, let's say I have a customer that can have any number of addresses in the database. Is there any way to list out each column of each address with perhaps a number as a part of the alias (e.g., columns like Customer Id, Name, Address_Street_1, Address_Street_2, etc)?
Thanks!
Not really - you really are doing a dynamic pivot. It's possible to use OPENROWSET to get to a dynamically generated query, but whether that's advisable, it's hard to say without seeing more about the business case.
First make a stored proc which does the dynamic pivot like I did on the StackExchange Data Explorer.
Basically, you generate dynamic SQL which builds the column list. This can only really be done in a stored proc. Which is fine for applciation calls.
But what about if you want to re-use that in a lot of different joins or ad hoc queries?
Then, have a look at this article: "Using SQL Servers OPENROWSET to break the rules"
You can now call your stored proc by looping back into the server and then getting the results into a rowset - this can be in a view!
The late Ken Henderson has some good examples of this in his excellent book: "The Guru's Guide to SQL Server Stored Procedures, XML, and HTML" (you got to love the little "Covers .NET!" on the cover which captures well the zeitgeist for 2002!).
He only covers the loopback part (with views and user-defined functions), the less verbose PIVOT syntax was not available until 2005, but PIVOTs can also be generated using a CASE statement as a characteristic function.
Obviously, this technique has caveats (I can't even do this on our production server).
Yes - use:
CREATE VIEW customer_addresses AS
SELECT t.customer_id,
t.customer_name,
a1.street AS address_street_1,
a2.street AS address_street_2
FROM CUSTOMER t
LEFT JOIN ADDRESS a1 ON a1.customer_id = t.customer_id
LEFT JOIN ADDRESS a2 ON a2.customer_id = t.customer_id
If you provided more info, it'd be easier to give you a better answer. It's possible you're looking to pivot data (turn rows into columns).
Simply put, no. Not without dynamically recreating the view every time you want to use it at least, that is.
But, what you can do is predefine, say, 4 address columns in your view, then populate the first four results of your one-to-many relation into those columns. It's not quite the dynamic view you want, but it's also much more stable/usable in my opinion.
When using multivalue parameters in sql reporting services is it more appropriate to implement the list filter using a filter on the dataset itself, the data region control or change the actual query that drives the dataset?
SSRS will support any scenario, so then I ask, is there a reason beyond the obvious of why this should be done at one level over another?
It makes sense to me that modifying the query itself and asking the RDBMS to handle the filtering would be most efficient but maybe I am missing something with respect to how the SSRS Data Processing Extension may handle this scenario?
You are correct. The way to go is to pass the parameters through to the database engine.
Reporting Services should only be ideally used to render content. The less data that you need to pass back to the client web browser, the faster the report will render.
You may find my answer to a similar post regarding using mulit-value parameters to be of use.
Passing multiple values for a single parameter in Reporting Services
Hope this helps but please feel free to pose any further questions you may have.
Cheers,
John
Using table-valued UDF is a good approach, but there is still one issue - in case if this function is called in many places of query, and even inside inner select, there can be performance problem. You can resolve this issue using table variable (or temp table eather):
DECLARE #Param (Value INT)
INSERT INTO #Param (Value)
SELECT Param FROM dbo.fn_MVParam(#sParameterString,',')
...
where someColumn IN(SELECT Value FROM #Param)
so function will be called only once.
Othe thing, if you don't use stored procedure, but embedded SQL query instead, you can just put MVP into query:
...
where someColumn IN(#Param)
...
Use the RDBMS to do the main filtering
SSRS provides filtering for the purposes on data driven display and/or dynamic display. Especially useful for sub reports etc