I am trying to filter values in a table using values in another table. Since USQL doesn't allow to use another table with the WHERE IN statement, my thoughts were to use a usql function to create a list of values and then pass that along to my main script.
Any ideas as to how I can pass the necessary variable? I would also be interested if there are other ways of aproaching this problem.
You should try to filter your dataset with SEMIJOIN OR ANTISEMIJOIN in USQL. Its the usql way dealing with IN/NOT IN
Check this
I ended up writing 2 c# functions as code behind to achieve what I want within a single script. The first function actually checks the input table for the values I need and creates a list. I use this function to declare a variable at the begining of my usql script. I then us this list as input to a second function that processes the values in my work table.
This is my current solution and it is working very well. I'm still new to U-SQL so if there is an easier way of doing this I would like to learn about it, so feel free to still contribute to this thread.
I am looking to write dynamic queries for an ArangoDB graph database and am wondering if there are best practices or standard approaches to doing it.
By 'dynamic queries' I mean that users would have the ability to build a query that is then executed on the dataset.
Methods that ArangoDB can support this could include:
Dynamically generate AQL queries by manually injecting bindvars
Write Foxx functions to deliver on supported queries, and have another Foxx function bind those together to build a response.
Write a workflow which extracts data into a temporary collection and then invokes Foxx functions to filter/sort the data to the desired outcome.
The queries would be very open ended, where someone would (for example):
Query all countries with population over 10,000,000
Sort countries by land in square kilometers
Pick the top 10 countries in land coverage
Select primary language spoken in each country
Count occurrences of each language.
That query alone is straight forward to execute, but if a user was able to [x] check or select from a range of supported query options, order them in their own defined way, and receive the output, it's a little more involved.
Are there some supported or recommended approaches to doing this?
My current approach would be to write blocks of AQL that delivered on each part, probably in a LET Q1 = (....), LET Q2 = (...) format, and then finally in the bottom of the query have a generic way of processing the queries to generate a response.
But I have a feeling that smart use of Foxx functions could help here as well, having Foxx-Query-Q1 and Foxx-Query-Q2 coded to support each query type, then an aggregation Foxx app that invoked the right queries in the right order to build the right response.
If anyone has seen best ways of doing this, it would be great to get some hints/advice.
Thanks!
I have following questions regarding Azure DocumentDB
According to this article, multiple functions have been added to
DocumentDB. Is there any way to get Date functions working? How can i
get the queries of type greater than some date working?
Is there any way to select top N results like 'Select top 10 * from users'?
According to Document playground , Order By will be supported in future. Is ther any other way around for now?
The application that I am developing requires certain number of results to be displayed that have been inserted recently. I need these functionalities within a stored procedure. The documents that I am storing in DocumentDB have a DateTime property. I require the above mentioned functionalities for my application to work. I have searched at documentation and samples. Please help if you know of any workaround.
Some thoughts/suggestions below:
Please take a look at this idea on how to store and query dates in DocumentDB (as epoch timestamps). http://azure.microsoft.com/blog/2014/11/19/working-with-dates-in-azure-documentdb-4/
To get top N results, set FeedOptions.MaxItemCount and read only one page, i.e., call ExecuteNextAsync() once. See https://msdn.microsoft.com/en-US/library/microsoft.azure.documents.linq.documentqueryable.asdocumentquery.aspx for an example. We're planning to add TOP to the grammar to make this easier in the future.
You can email me at arramac at microsoft dot com to get early access to Order By right away. This is planned for broad release shortly.
Please note that stored procedures are best used when you have a write operation(s). You'll be able to better throughput on reads when you query directly.
Is it possible to transform the returned data from a Find query in MongoDB?
As an example, I have a first and last field to store a user's first and last name. In certain queries, I wish to return the first name and last initial only (e.g. 'Joe Smith' returned as 'Joe S'). In MySQL a SUBSTRING() function could be used on the field in the SELECT statement.
Are there data transformations or string functions in Mongo like there are in SQL? If so can you please provide an example of usage. If not, is there a proposed method of transforming the data aside from looping through the returned object?
It is possible to do just about anything server-side with mongodb. The reason you will usually hear "no" is you sacrifice too much speed for it to make sense under ordinary circumstances. One of the main forces behind PyMongo, Mike Dirolf with 10gen, has a good blog post on using server-side javascript with pymongo here: http://dirolf.com/2010/04/05/stored-javascript-in-mongodb-and-pymongo.html. His example is for storing a javascript function to return the sum of two fields. But you could easily modify to return the first letter of your user name field. The gist would be something like:
db.system_js.first_letter = "function (x) { return x.charAt(0); }"
Understand first, though, that mongodb is made to be really good at retrieving your data, not really good at processing it. The recommendation (see for example 50 tips and tricks for mongodb developers from Kristina Chodorow by Oreilly) is to do what Andrew tersely alluded to doing above: make a first letter column and return that instead. Any processing can be more efficiently done in the application.
But if you feel that even querying for the fullname before returning fullname[0] from your 'view' is too much of a security risk, you don't need to do everything the fastest possible way. I'd avoided map-reduce in mongodb for awhile because of all the public concerns about speed. Then I ran my first map reduce and twiddled my thumbs for .1 seconds as it processed 80,000 10k documents. I realize in the scheme of things, that's tiny. But it illustrates that just because it's bad for a massive website to take a performance hit on some server side processing, doesn't mean it would matter to you. In my case, I imagine it would take me slightly longer to migrate to Hadoop than to just eat that .1 seconds every now and then. Good luck with your site
The question you should ask yourself is why you need that data. If you need it for display purposes, do that in your view code. If you need it for query purposes, then do as Andrew suggested, and store it as an extra field on the object. Mongo doesn't provide server-side transformations (usually, and where it does, you usually don't want to use them); the answer is usually to not treat your data as you would in a relational DB, but to use the more flexible nature of the data store to pre-bake your data into the formats that you're going to be using.
If you can provide more information on how this data should be used, then we might be able to answer a little more usefully.
In my travels in Oracle, the 'stragg' function, or 'String Aggregator' was life-saving when I had to create dynamic SQL queries on the fly.
You can read up about it here: http://www.oratechinfo.co.uk/delimited_lists_to_collections.html
The basic use of it was:
select stragg(fruit) from food;
fruit
-----------
apple,pear,banana,strawberry
1 row(s) returned
So simple to use, concatenating chr(13) turned it into a long list, and selecting information from system tables gave a 5 minute solution to dynamically generated SQL, e.g. auditing triggers.
Now I've been charged with transferring oracle functionality related to auditing into Sybase, and a function similar to Stragg would be ideal for this purpose.
E.g.
select #my_table = 'table_of_fruit'
select 'insert into '+#mytable+'_copy (' +char(10)
+ stragg(c.name) +char(10)
+ 'select '
+ stragg('inserted.'+c.name) + char(10)
+ 'from '+#mytable
from syscolumns c
where objectid(#mytable) = c.id
------------------------------------------
insert into table_of_fruit_copy
(fruit, sweetness, price)
select fruit, sweetness,price
from inserted
Done. Simple.
Except I don't know how to get a string-aggregation function working in Sybase.
Does anyone know of an attempt to do this kind of thing, or code that could work the same as stragg that could be used in this way?
The alternative at the moment is printing code based on complex cursors and such (sample LOC: 500), or select statements combining static strings and columns from user tables (sample LOC: 200). Stragg would severely reduce the complexity of this code, and would be a great deal of help in the future (sample LOC: who knows, maybe 50?)
p.s. I'm calling these selects through a shell script then piping them to file, then running the file through iSQL. Not the nicest solution, but it's better than the alternatives.
There are three separate answers
Question
You have made comments about simplicity, which need to be addressed before we get to the solution.
It is a common requirement to be able to take a delimited list of values, say A,B,C,D, and treat this data like it was a set of rows in a table, or vice versa
This one of the Top Ten Worst Programming Practices I read about recently.
In general, Sybase types tend to be somewhat more academically and Relationally qualified than Oracle types, so we simply do not do that sort of thing in SybaseLand or DB2Land.
In 20 years of working with Sybase, I have had to code that as part of my project just once, and that was for non-technical Auditor who loaded the result set into MS Access.
On the other hand, I have had to code that at least 12 times, when producing text files for importation into Oracle databases (fulfilling external requirements is outside my project, but I satisfy any such requirement free). Obviously the target databases were sub-standard and non-relational (loading a column with more than one datum breaks 1NF, and creates Update Anomalies), which is typical of what Oracle types have to do to get some speed.
Therefore, no, it is not simplicity, at least in the sense of that principle. It is by definition, complexity.
Your reference to "arrays" is incorrect. All commercial dbms handle arrays, according to the ISO/IEC/ANSI SQL (STRAGGR and LIST operators are non-standard SQL, therefore not SQL). Sybase is very strong in processing arrays. If it was an array, you would not need special hand coding to handle it (and you do, as per your question). This is not an array, there is no definition to the cells. This is a single concatenated scalar string.
Pivoting is an entirely different process, which uses set-processing; it does not require row-processing. (I understand on good authority, that Oracle is hopeless at scalar subqueries, and thus Oracle people are used to writing them as [very inefficient] joins or inline views, and then filtering: all that can be elevated to set-processing via scalar subqueries, and it will perform much faster. Particularly your Pivots.)
Even the author in your link posts as follows. Please familiarise yourself with the caveats:
It's as simple as this: If you want to have a system with no logical limitation in the number of data elements passed to a given process, then forget the following mechanisms! They are simply the wrong way to approach the problem.
Therefore, know whatever you are doing is sub-standard, non-relational, and limited; and go ahead with your eyes open. No use pretending that: it will not break; it is not limited; it is an "array"; or that Sybase doesn't have a neat little function that Oracle has. Any professional will see through all that. And if the string length is exceeded, for God's sake send some indicator back to the caller ("!Exceeded" in the string) identifying that condition.
Essentially you are turning the set-processing engine on its head, and forcing it into row-processing mode, so it will be very slow. A WHILE loop is distinctly faster than a cursor, but both are in the same class, row-processors.
The alternative at the moment is printing code based on complex cursors and such
What 200 or 500 LoC ? It is possible I am missing something, but my code is the same few lines of code identified under "Using a Table Function" in your link. Maximum 20, if you count nice formatting; the loop; initialisation; error handling. There is nothing "complex" about it. Do the exact reverse to cancatenate a single string from multiple rows. We use stored procedures for this (which oracle does not have, really, PL/SQL is a different animal). If you have ASE 15.0.2 or greater, you can use a User Defined Function, which you can then use in place of a column. Stored procs are better for true arrays.
the concatenation operator in Sybase is the plus sign. For reversal (decomposing the CSV string) you need CHARINDEX and SUBSTRING functions
You may need the Function Reference Manual, if for nothing else, to avoid writing code where we have functions.
Likewise, we do not have a RANK() function. We are quite happy with the 4 lines of code requires for the subquery. It is only required for Oracle because subqueries are crippled.
Ok, I have answered your question, Now to address the approaches.
You will be aware that code using Oracle Extensions to the SQL standard will need to be changed.
Sybase is way more automated than Oracle; if you familiarise yourself with its feature set, in many instances, you can get the same result (as you did in Oracle) without writing any code. Writing code-for-code blocks is the chain gang, rock-breaking method of building roads, in the context of bulldozers. Even if your company had good reason to use that method, you need to the aware that features work quite differently, eg. triggers, which is why I am posting so much detail.
Another issue that will annoy you is that Oracle isn't really ANSI SQL compliant (stretches the definitions in many places, in order to appear to be compliant), and Sybase, given its customer base, is rigidly SQL compliant. So in addition to the same function working differently, or in a different deployment, you need to be aware that code changes may be required to elevate Oracle code to ANSI compliance levels, just to execute on an ANSI SQL compliant platform.
I am not sure if you are trying to write code for the content of a trigger, or if you are trying to capture the changes to a database. I will provide both answers.
Auditing
Capture Changes to Database
We have an very robust, fast and configurable Auditing subsystem, fit for high volumes and banking level auditing requirements. Get your DBA to setup the sybaudit (separate) database, and to configure exactly what changes need to be captured. This facility will perform much faster than any code you or I can write in a trigger (as much as 100 times faster than your row-by-processing required for the above, as it is executed within the engine, within your executing thread). And of course the setup time is a fraction of your coding time.
Triggers
Again, I am not sure exactly what you are trying to achieve, but assuming you want to copy every insert to some table to a COPY of that table (inside the Trigger), that example code you have provided will not work (and I am not counting syntax issues).
Speaking to your example, you need to do way more work, to deal with the different datatypes; column sizes; precisions; scale; etc. And perhaps the UPDATE() function to identify which columns have changed (for an UPDATE trigger of course). If all you are trying to do is convert the various datatypes to strings, check the CONVERT() function.
Triggers are transactional.
Never place row-processing code in a Trigger (it will strangle the table)
You can't place Dynamic SQL in a Trigger.
But in Sybase even that is not necessary. Refer to the User Guide, chapter 19 is devoted to Triggers, with several variations, and examples. Inside the trigger, you should be able to simply:
INSERT table_copy
SELECT column_list -- never use * unless you want the db fixed in cement
FROM inserted
If you are trying to copy the inserts to all tables into one Audit table, then beware. Then I understand your example a little bit more. You will be forcing a highly Symmetric Muli-Threading server (oracle is not a server in the architecture sense) into single-threading through your table. Auditing is multi-threaded.
Last, the use of manual methods of any kind is not required, so if you could expand a bit more on your PS, what the requirement you are trying to fulfil is, I can identify the programmatic method for you. It appears you are trying to use the PL/SQL approach (which is very limited).
Just use the LIST() function. It's a direct replacement for stragg() function. Example:
SELECT LIST(state, ', ') FROM cities
Result:
name
CA, CA, MA, NY