So I'm using the Entity Framework and we have a modal for a table called TPM_PROJECTVERSIONNOTES. This table has a column called NOTEID which is a number. Right now, when we create a new row, we get the next available number with this code:
note.NOTEID = (from n in context.TPM_PROJECTVERSIONNOTES
orderby n.NOTEID descending
select n.NOTEID).Max() + 1;
To me, this seems incredibly hacky (I mean you have to do an entire SQL query just to get the next value). Plus, it's incredibly dangerous; it's not thread safe or transaction safe. I've already found 9 instances in the DB that have the same NOTEID! Good thing no one even thought to put a UNIQUE constraint on that column... sigh.
So anyway, I've added a new sequence to the database:
CREATE SEQUENCE TPM_PROJECTVERSIONNOTES_SEQ START WITH 732 INCREMENT BY 1;
Now my question:
How do I instruct the Entity framework to use TPM_PROJECTVERSIONNOTES_SEQ.nextval when inserting a row into this table? Basically, I just don't want to specify a NOTEID at all and I want the framework to take care of it for me. It's been suggested I use a trigger, but I think this is a bit hacky and would rather have to Entity framework just create the correct SQL in the first place. I'm using Oracle 11g for this.
While this may still fall into what you call the 'hacky' category, you can avoid using triggers to call the nextval, but you must utilize a stored procedure to handle the insert (whereas it will call the nextval in lieu of using a TRIGGER). (I guess this could fall more into a TAPI/XAPI category)
Check out the recent article
TECHNOLOGY: Oracle Data Provider for .NET
it explains (and contains samples) to using a stored procedure to handle the insert, calling the sequence, and mapping it back to the ODP EF BETA.
This obviously does not have the ODP EF Beta do the SQL for nextval, but it is an alternative. (look at this forum, it does appear that most of the EF Oracle frameworks fall victim to this-- devart etc {https://forums.oracle.com/forums/thread.jspa?threadID=2184372} )
Related
I have an existing db that I am using entityframework 6 Code-First on to work with. A requirement though is that all work with the db has to be via stored procedures. So I started out using the mapping that is new in 6.0:
modelBuilder.Entity<Post>().MapToStoredProcedures();
The issue is that this only supports mapping Insert, Update, and Delete sp's not the select sp's, I need to be able to us a sp to select. (I do not have access to edit any of the existing sp's)
My poco's have attributes on them specifying the column name's to use using the column attribute. Apparently though the built in mapping does not support using those unless you are doing a direct selection on the table via a dbset object.
Originally I had (which worked):
return (from c in DataContext.Current.AgeRanges orderby c.StartAge select c);
Then to switch it to the sp I tried (using the database sqlquery call):
return DataContext.Current.Database.SqlQuery<AgeRange>("[DIV].[GetAgeRangesList]").AsQueryable();
This returned valid objects, but none of the columns marked with the Column attribute had anything in them.
Then I tried (thinking since it was against the actual dbset object I'd get the column mapping):
return DataContext.Current.AgeRanges.SqlQuery("[DIV].[GetAgeRangesList]").ToList().AsQueryable();
Nope, this instead gave me an error that one of the properties in the POCO object (one of the Column attribute ones) was not found in the returned recordset.
So the question is, in entity framework (or best solution outside of that) what is the best way to call a stored procedure and map the results to objects and have that mapping respect the column attribute on the properties?
I would even be willing to use an old school Table object and a SqlCommand object to fill it, if I had a fast easy way to then map the objects that respects the Column Attribute.
SqlQuery does not honor Column attribute. If the names of the columns of the returned result set match the names of the properties of the entity the properties should be set accordingly. Note however that SqlQuery does only minimal amount of work (for instance it does not support relationships (.Include)) so you are limiting yourself if you decide using stored procedures for queries.
Enhancing SqlQuery to use ColumnName attributes is being tracked here: https://entityframework.codeplex.com/workitem/233 - feel free to upvote this codeplex item.
I'd like to use flyway for a DB update with the situation that an DB already exists with productive data in it. The problem I'm looking at now (and I did not find a nice solution yet), is the following:
There is an existing DB table with numeric IDs, e.g.
create table objects ( obj_id number, ...)
There is a sequence "obj_seq" to allocate new obj_ids
During my DB migration I need to introduce a few new objects, hence I need new
object IDs. However I do not know at development time, what ID
numbers these will be
There is a DB trigger which later references these IDs. To improve performance I'd like to avoid determine the actual IDs every time the trigger runs but rather put the IDs directly into the trigger
Example (very simplified) of what I have in mind:
insert into objects (obj_id, ...) values (obj_seq.nextval, ...)
select obj_seq.currval from dual
-> store this in variable "newID"
create trigger on some_other_table
when new.id = newID
...
Now, is it possible to dynamically determine/use such variables? I have seen the flyway placeholders but my understanding is that I cannot set them dynamically as in the example above.
I could use a Java-based migration script and do whatever string magic I like - so, that would be a way of doing it, but maybe there is a more elegant way using SQL?
Many thx!!
tge
If the table you are updating contains only reference data, get rid of the sequence and assign the IDs manually.
If it contains a mix of reference and user data, you need to select the id based on values in other columns.
My situation
I have a c# object which contains some lists. One of these lists are for example a list of tags, which is a list of c# "SystemTag"-objects. I want to instantiate this object the most efficient way.
In my database structure, I have the following tables:
dbObject - the table which contains some basic information about my c# object
dbTags - a list of all available tabs
dbTagConnections - a list which has 2 fields: TagID and ObjectID (to make sure an object can have several tags)
(I have several other similar types of data)
This is how I do it now...
Retrieve my object from the DB using an ID
Send the DB object to a "Object factory" pattern, which then realise we have to get the tags (and other lists). Then it sends a call to the DAL layer using the ID of our C# object
The DAL layer retrieves the data from the DB
These data are send to a "TagFactory" pattern which converts to tags
We are back to the Object Factory
This is really inefficient and we have many calls to the database. This especially gives problems as I have 4+ types of lists.
What have I tried?
I am not really good at SQL, but I've tried the following query:
SELECT * FROM dbObject p
LEFT JOIN dbTagConnection c on p.Id= c.PointId
LEFT JOIN dbTags t on c.TagId = t.dbTagId
WHERE ....
However, this retreives as many objects as there are tagconnections - so I don't see joins as a good way to do this.
Other info...
Using .NET Framework 4.0
Using LINQ to SQL (BLL and DAL layer with Factory patterns in the BLL to convert from DAL objects)
...
So - how do I solve this as efficient as possible? :-) Thanks!
At first sight I don't see your current way of work as "inefficient" (with the information provided). I would replace the code:
SELECT * FROM dbObject p
LEFT JOIN dbTagConnection c on p.Id= c.PointId
LEFT JOIN dbTags t on c.TagId = t.dbTagId
WHERE ...
by two calls to the DALs methods, first to retrieve the object main data (1) and one after that to get, only, the data of the tags related (2) so that your factory can fill-up the object's tags list:
(1)
SELECT * FROM dbObject WHERE Id=#objectId
(2)
SELECT t.* FROM dbTags t
INNER JOIN dbTag Connection c ON c.TagId = t.dbTagId
INNER JOIN dbObject p ON p.Id = c.PointId
WHERE p.Id=#objectId
If you have many objects and the amount of data is just a few (meaning that your are not going to manage big volumes) then I would look for a ORM based solution as the Entity Framework.
I (still) feel comfortable writing SQL queries in the DAOs to have under control all queries being sent to the DB server, but finally it is because in our situation is a need. I don't see any inconvenience on having to query the database to recover, first, the object data (SELECT * FROM dbObject WHERE ID=#myId) and fill the object instance, and then query again the DB to recover all satellite data that you may need (the Tags in your case).
You have be more concise about your scenario so that we can provide valuable recommendations for your particular scenario. Hope this is useful you you anyway.
We used stored procedures that returned multiple resultsets, in a similar situation in a previous project using Java/MSSQL server/Plain JDBC.
The stored procedure takes the ID corresponding to the object to be retrieved, return the row to build the primary object, followed by multiple records of each one-to-many relationship with the primary object. This allowed us to build the object in its entirety in a single database interaction.
Have you thought about using the entity framework? You would then interact with your database in the same way as you would interact with any other type of class in your application.
It's really simple to set up and you would create the relationships between your database tables in the entity designer - this will give you all the foreign keys you need to call related objects. If you have all your keys set up in the database then the entity designer will use these instead - creating all the objects is as simple as selecting 'Create model from database' and when you make changes to your database you simply right-click in your designer and choose 'update model from database'
The framework takes care of all the SQL for you - so you don't need to worry about that; in most cases..
A great starting place to get up and running with this would be here, and here
Once you have it all set up you can use LINQ to easily query the database.
You will find this a lot more efficient than going down the table adapter route (assuming that's what you're doing at the moment?)
Sorry if i missed something and you're already using this.. :)
As far I guess, your database exists already and you are familiar enough with SQL.
You might want to use a Micro ORM, like petapoco.
To use it, you have to write classes that matches the tables you have in the database (there are T4 generator to do this automatically with Visual Studio 2010), then you can write wrappers to create richer business objects (you can use the ValueInjecter to do it, it is the simpler I ever used), or you can use them as they are.
Petapoco handles insert / update operations, and it retrieves generated IDs automatically.
Because Petapoco handles multiple relationships too, it seems to fit your requirements.
I need to be able to run a query such as
SELECT * FROM atable WHERE MyFunc(afield) = "some text"
I've written MyFunc in a VB module but the query results in "Undefined function 'MyFunc' in expression." when executed from .NET
From what I've read so far, functions in Access VB modules aren't available in .NET due to security concerns. There isn't much information on the subject but this avenue seems like a daed end.
The other possibility is through the CREATE PROCEDURE statement which also has precious little documentation: http://msdn.microsoft.com/en-us/library/bb177892%28v=office.12%29.aspx
The following code does work and creates a query in Access:
CREATE PROCEDURE test AS SELECT * FROM atable
However I need more than just a simple select statement - I need several lines of VB code.
While experimenting with the CREATE PROCEDURE statement, I executed the following code:
CREATE PROCEDURE test AS
Which produced the error "Invalid SQL statement; expected 'DELETE', 'INSERT', 'PROCEDURE', 'SELECT', or 'UPDATE'."
This seems to indicate that there's a SQL 'PROCEDURE' statement, so then I tried
CREATE PROCEDURE TEST AS PROCEDURE
Which resulted in "Syntax error in PROCEDURE clause."
I can't find any information on the SQL 'PROCEDURE' statement - maybe I'm just reading the error message incorrectly and there's no such beast. I've spent some time experimenting with the statement but I can't get any further.
In response to the suggestions to add a field to store the value, I'll expand on my requirements:
I have two scenarios where I need this functionality.
In the first scenario, I needed to enable the user to search on the soundex of a field and since there's no soundex SQL function in Access I added a field to store the soundex value for every field in every table where the user wants to be able to search for a record that "soundes like" an entered value. I update the soundex value whenever the parent field value changes. It's a fair bit of overhead but I considered it necessary in this instance.
For the second scenario, I want to normalize the spacing of a space-concatenation of field values and optionally strip out user-defined characters. I can come very close to acheiving the desired value with a combination of TRIM and REPLACE functions. The value would only differ if three or more spaces appeared between words in the value of one of the fields (an unlikely scenario). It's hard to justify the overhead of an extra field on every field in every table where this functionality is needed. Unless I get specific feedback from users about the issue of extra spaces, I'll stick with the TRIM & REPLACE value.
My application is database agnostic (or just not very religious... I support 7). I wrote a UDF for each of the other 6 databases that does the space normalization and character stripping much more efficiently than the built-in database functions. It really annoys me that I can write the UDF in Access as a VB macro and use that macro within Access but I can't use it from .NET.
I do need to be able to index on the value, so pulling the entire column(s) into .NET and then performing my calculation won't work.
I think you are running into the ceiling of what Access can do (and trying to go beyond). Access really doesn't have the power to do really complex TSQL statements like you are attempting. However, there are a couple ways to accomplish what you are looking for.
First, if the results of MyFunc don't change often, you could create a function in a module that loops through each record in atable and runs your MyFunc against it. You could either store that data in the table itself (in a new column) or you could build an in-memory dataset that you use for whatever purposes you want.
The second way of doing this is to do the manipulation in .NET since it seems you have the ability to do so. Do the SELECT statement and pull out the data you want from Access (without trying to run MyFunc against it). Then run whatever logic you want against the data and either use it from there or put it back into the Access database.
Why don't you want to create an additional field in your atable, which is atable.afieldX = MyFunc(atable.afield)? All what you need - to run UPDATE command once.
You should try to write a SQL Server function MyFunc. This way you will be able to run the same query in SQLserver and in Access.
A few usefull links for you so you can get started:
MSDN article about user defined functions: http://msdn.microsoft.com/en-us/magazine/cc164062.aspx
SQLServer user defined functions: http://www.sqlteam.com/article/intro-to-user-defined-functions-updated
SQLServer string functions: http://msdn.microsoft.com/en-us/library/ms181984.aspx
What version of JET (now called Ace) are you using?
I mean, it should come as no surprise that if you going to use some Access VBA code, then you need the VBA library and a copy of MS Access loaded and running.
However, in Access 2010, we now have table triggers and store procedures. These store procedures do NOT require VBA and in fact run at the engine level. I have a table trigger and soundex routine here that shows how this works:
http://www.kallal.ca/searchw/WebSoundex.htm
The above means if Access, or VB.net, or even FoxPro via odbc modifies a row, the table trigger code will fire and run and save the soundex value in a column for you. And this feature also works if you use the new web publishing feature in access 2010. So, while the above article is written from the point of view of using Access Web services (available in office 365 and SharePoint), the above soundex table trigger will also work in a stand a alone Access and JET (ACE) only application.
I will explain problem with an example:
There is two table in my database, named entry, tags
There is a column named ID_ENTRY in both table. When I add a record to table, entry, I have to take the ID_ENTRY of last added record and add it to table, tags. How can I do it?
The only way to do this is with multiple statements. Using dynamic sql you can do this by separating each statement in your query string with a semi-colon:
"DECLARE #ID int;INSERT INTO [Entry] (...) VALUES ...; SELECT #ID = scope_identity();INSERT INTO [TAGS] (ID_ENTRY) VALUES (#ID);"
Make sure you put this in a transaction to protect against concurrency problems and keep it all atomic. You could also break that up into two separate queries to return the new ID value in the middle if you want; just make sure both queries are in the same transaction.
Also: you are using parameterized queries with your dynamic sql, right? If you're not, I'll personally come over there and smack you 10,000 times with a wet noodle until you repent of your insecure ways.
Immediatly after executing the insert statement on first table, you should query ##IDENTITY doing "SELECT ##identity". That will retrieve the last autogenerated ID... and then just insert it on the second table.
If you are using triggers or something that inserts rows... this may be not work. Use Scope_Identity() instead of ##IDENTITY
I would probably do this with an INSERT trigger on the named entry table, if you have all of the data you need to push to the tags table available. If not, then you might want to consider using a stored procedure that creates both inside a transaction.
If you want to do it in code, you'll need to be more specific about how you are managing your data. Are you using DataAdapter, DataTables, LINQ, NHibernate, ...? Essentially, you need to wrap both inserts inside a transaction of some sort so that either inserts get executed or neither do, but the means to doing that depend on what technology you are using to interact with the database.
If you use dynamic sql, why not use Linq to Entity Framework, now EF is the recommend data access technology from Microsoft (see this post Clarifying the message on L2S Futures from ADO.NET team blog), and if you do an insert with EF the last identity id will available for you automatically, I use it all the time it's easy.
Hope this helps!
Ray.