Is there a way to do
"UPDATE Item SET start_date = CURRENT_TIMESTAMP" ?
in Nhibernate without using hql/sql.
I am trying to avoid hql/sql because the rest of my code is in criteria. I want to do something like :
var item = session.get<Item>(id)
item.start_date = current_timestamp
There are two ways and sql is correct one.
Either you will
load all entities, change, update and commit, or
write sql query and let dbms handle most of the work
I am trying to avoid hql/sql because the rest of my code is in criteria
That is not a valid argument. Criteria is an API intended for relational search, and it does not support mass updates.
Different tasks, different APIs.
In this case, you can use either HQL or SQL, as the syntax is the same. I recommend the former, because you'll be using your entity/property names instead of table/column ones.
Related
I am trying to create an SAP data query using SQVI (or SQ01) to display all entries that meet certain criteria. I can use the 'Selection Fields' tab to have a user specify any of these parameters, but I want to be able to query the data with more complex conditions such as a nested 'AND'/'OR'. I have researched the question for a couple hours and have yet to find a solution that works. Here is an example simplified query that I would like to do, written in SQL form:
SELECT t0.name, t0.birthYear, t1.grade, t1.county
FROM t0
INNER JOIN t1 on t0.personID = t1.personID
WHERE t0.name = 'Bob'
AND t0.birthyear = 2000
AND (t1.grade = 12
OR t1.county <> 'Cook');
Now the tricky part is figuring out how to do a nested 'AND' and 'OR' in SQVI. At first, I pulled all the data without these conditions, exported it to Excel, and then performed this logic to get the correct entries that meet these criteria. However, I do not want to do this every time, as it is highly repetitive and there HAS TO be some solution within the SAP environment. Ideally, I would be able to create a query that I can share with co-workers to execute once a week, where they don't need to enter any values to test against 'name', 'birthyear', 'grade', or 'county'. They should be able to type in the code for this query and hit execute, and it should spit out all of the entries that meet all the criteria. I want to be able to hard-code the testing parameters in this instance.
Let me know if this is even possible! If it's not possible using SQVI, what would I need access to in order to do a complex conditional query like this? I do not have write-access on the data, so I am not authorized to use 'DBACOCKPIT' to write the query as SQL (which would be so much simpler).
I need do a filtering query with some query parameter. I need that if the query parameter is null, the condition of the query (= or LIKE, for example) is not evaluated and return me everything. I'm using R2DBC and I don't find a way to solve it.
If you are using Spring Data R2dbc, besides the above raw SQL query, you can use R2dbcOperations to compose Criteria by condition freely.
The following is an example.
template
.select(Post.class)
.matching(
Query
.query(where("title").like("%" + name + "%"))// extract where here you can assemble the query condition freely.
.limit(10)
.offset(0)
)
.all();
Additionally using R2dbcRepository and convention-based method, try to use a default value in the like(eg. set the null to empty string "" in like) to save work to determine if it is a null value in sql.
A general prepared statement which would work might be:
SELECT *
FROM yourTable
WHERE col = ? or ? IS NULL;
In the event that you bind a NULL value to the ? from your obfuscation layer, the WHERE clause would always be true, returning all records in the table.
If you prefer doing this with a "static SQL statement" (meaning you use a single SQL string for all possible bind values), then, in Oracle, it's probably optimal to use NVL() to profit from an Oracle optimiser feature, as explained in this article, irrespective of whether you're using R2DBC:
SELECT *
FROM t
WHERE col = nvl(:bind, col)
However, a query like yours is often best implemented using dynamic SQL, such as supported by a third party library like jOOQ:
Flux<TRecord> result =
Flux.from(ctx
.selectFrom(T)
.where(bind == null ? noCondition() : T.COL.eq(bind))
);
You can obviously also do this yourself, directly with R2DBC and your own dynamic SQL library, or any other such library.
Disclaimer: I work for the company behind jOOQ.
I want to add this part to my current sql in Active-Recod-class:
JOIN
(SELECT product_id, max(angle) AS max_angle
FROM image t1
WHERE width = 100 AND height = 200
GROUP BY product_id) AS t1 ON (t1.product_id = mv_products.id)
What would be the correct approach to manage this?
Is the only way to download subquery-class github? https://github.com/NTICompass/CodeIgniter-Subqueries
?
This is exactly the kind of thing that you shouldn't do via CI's Active Record (Query Builder). It's there to help you with simple queries, not to force you to use it.
This is a custom query as such, should be executed via $this->db->query().
With the currently released versions of CI, you wouldn't be able to do that via AR anyway because join() will break that subquery while trying to escape it (it assumes that you're only passing two field names). CI 3.0-dev allows you to disable field name escaping, but again - you shouldn't use the query builder for what you're asking here.
suppose my LINQ query is like
var qry = from c in nwEntitiesContext.CategorySet.AsEnumerable()
let products = this.GetProducts().WithCategoryID(c.CategoryID)
select new Model.Category
{
ID = c.CategoryID,
Name = c.CategoryName,
Products = new Model.LazyList<Core.Model.Product>(products)
};
return qry.AsQueryable();
i just want to know what query it will generate at runtime....how to see what query it is generating from VS2010 IDE when we run the code in debug mode....guide me step by step.
There is not much to see here - it will just select all fields from the Category table since you call AsEnumerable thus fetching all the data from the Category table into memory. After that you are in object space. Well, depending on what this.GetProducts() does - and my guess it makes another EF query fetching the results into memory. If that's the case, I would strongly recommend you to post another question with this code and the code of your GetProducts method so that we can take a look and rewrite this in a more optimal way. (Apart from this, you are projecting onto a mapped entity Model.Category which again won't (and should not) work with Linq-to-Entities.)
Before reading into your query I was going to recommend doing something like this:
string sqlQueryString = ((ObjectQuery)qry).ToTraceString();
But that won't work since you are mixing Linq-to-Entities with Linq-to-objects and you will actually have several queries executed in case GetProducts queries EF. You can separate the part with your EF query and see the SQL like this though:
string sqlString = nwEntitiesContext.CategorySet.ToTraceString();
but as I mentioned earlier - that would just select everything from the Categories table.
In your case (unless you rewrite your code in a drastic way), you actually want to see what queries are run against the DB when you execute the code and enumerate the results of the queries. See this question:
exact sql query executed by Entity Framework
Your choices are SQL Server Profiler and Entity Framework Profiler. You can also try out LinqPad, but in general I still recommend you to describe what your queries are doing in more detail (and most probably rewrite them in a more optimal way before proceeding).
Try Linqpad
This will produce SELECT * FROM Categories. Nothing more. Once you call AsEnumerable you are in Linq-to-objects and there is no way to get back to Linq-to-entities (AsQueryable doesn't do that).
If you want to see what query is generated use SQL Profiler or any method described in this article.
So I'm extremely new to Linq in .Net 3.5 and have a question. I use to use a custom class that would handle the following results from a store procedure:
Set 1: ID Name Age
Set 2: ID Address City
Set 3: ID Product Price
With my custom class, I would have received back from the database a single DataSet with 3 DataTables inside of it with columns based on what was returned from the DB.
My question is how to I achive this with LINQ? I'm going to need to hit the database 1 time and return multiple sets with different types of data in it.
Also, how would I use LINQ to return a dynamic amount of sets depending on the parameters (could get 1 set back, could get N amount back)?
I've looked at this article, but didn't find anything explaining multiple sets (just a single set that could be dynamic or a single scalar value and a single set).
Any articles/comments will help.
Thanks
I believe this is what you're looking for
Linq to SQL Stored Procedures with Multiple Results - IMultipleResults
I'm not very familiar with LINQ myself but here is MSDN's site on LINQ Samples that might be able to help you out.
EDIT: I apologize, I somehow missed the title where you mentioned you wanted help using LINQ with Stored Procedures, my below answer does not address that at all and unfortunately I haven't had the need to use sprocs with LINQ so I'm unsure if my below answer will help.
LINQ to SQL is able hydrate multiple sets of data into a object graph while hitting the database once. However, I don't think LINQ is going to achieve what you ultimately want -- which as far as I can tell is a completely dynamic set of data that is defined outside of the query itself. Perhaps I am misunderstanding the question, maybe it would help if you provide some sample code that your existing application is using?
Here is a quick example of how I could hydrate a anonymous type with a single database call, maybe it will help:
var query = from p in db.Products
select new
{
Product = p,
NumberOfOrders = p.Orders.Count(),
LastOrderDate = p.Orders.OrderByDescending().Take(1).Select(o => o.OrderDate),
Orders = p.Orders
};