That may be a silly question, but I just can't find any answer to it.
I have a simple query like 'SELECT * FROM table WHERE (x=a AND y=b) OR z=c' and I just can't find out how to implement that in ZF2.
I found a lot of information on Predicates and Where objects, but I can't find out how to combine that information into a query consisting of AND and OR.
I'd really appreciate it if someone can point me to the right direction.
If you want to add them using AND, you can simply pass them into the select object using an array, for example:
$select->where(array(
'type' => 'test,
'some_field' => '1'
));
If you want more complex Where queries, then you can use a Where object to build up a query:
$where = new \Zend\Db\Sql\Where();
$where->addPredicate(
new \Zend\Db\Sql\Predicate\Like('some_field', '%'.$value.'%')
)
->OR->->equalTo('my_field', 'bob')
->AND->equalTo('my_field', 'hello');
$select->where($where);
Related
I have the following entities in Entity Framwork 5 (C#):
OrderLine - Id, OrderId, ProductName, Price, Deleted
Order - Id, CustomerId, OrderNo, Date
Customer - Id, CustomerName
On the order search screen the user can enter the following search values:
ProductName, OrderNo, CustomerName
For Example they might enter:
Product Search Field: 'Car van bike'
Order Search Field: '100 101 102'
Customer Search Field: 'Joe Jack James'
This should do a OR search (ideally using linq to entities) for each entered word, this example would output the following where sql.
(ProductName like 'Car' Or ProductName like 'van' Or ProductName like 'bike') AND
(OrderNo like '100' Or OrderNo like '101' Or OrderNo like '102') AND
(CustomerName like 'Joe' Or CustomerName like 'Jack' Or CustomerName like 'James')
I want to do this using linq to entities, i am guessing this would need to be some sort of dynamic lambda builder as we don't know how many words the user might enter into each field.
How would i go about doing this, i have had a quick browse but cant see anything simple.
You can build a lambda expression using Expression Trees . What you need to do is split the value and build the expression . Then you can convert in in to a lambda expression like this,
var lambda = Expression.Lambda<Func<object>>(expression);
Here is an example
There are 2 basic approaches to Dynamic Expressions and Queries in LINQ.
3 if you count using Json as the approach to get a lambda expression. => Akash Kava post
a) String Dynamic Lambda
System.Linq.Dynamic can be found at following links
http://msdn.microsoft.com/en-US/vstudio/bb894665.aspx
http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx
http://www.scottgu.com/blogposts/dynquery/dynamiclinqcsharp.zip
b) Build Expression trees
More powerful but harder to master...
Build expressions trees with code found here:
http://msdn.microsoft.com/en-us/library/system.linq.expressions.aspx
an alternate approach is predicate builder but it isnt really that dynamic.
but can deal with the OR type scenario you give as example.
http://www.albahari.com/nutshell/predicatebuilder.aspx
I would recomend to go slightly different way from answers above and use EntitySQL as it is trivial to build SQL-like string with dynamic conditions.
http://msdn.microsoft.com/en-us/library/bb738683.aspx
Disclaimer: I am author of Entity REST SDK.
You can look at Entity REST SDK at http://entityrestsdk.codeplex.com
You can query using JSON syntax as shown below,
/app/entity/account/query?query={AccountID:2}&orderBy=AccountName
&fields={AccountID:'',AcccountName:''}
You can use certain extensions provided to convert JSON to lambda.
And here is details of how JSON is translated to Linq. http://entityrestsdk.codeplex.com/wikipage?title=JSON%20Query%20Language&referringTitle=Home
Current Limitations of OData v3
Additionally, this JSON based query is not same as OData, OData does not yet support correct way to search using navigation properties. OData lets you search navigation property inside a selected entity for example Customer(1)/Addresses?filter=..
But here we support both Any and Parent Property Comparison as shown below.
Example, if you want to search for List of Customers who have purchased specific item, following will be query
{ 'Orders:Any': { 'Product.ProductID:==': 2 } }
This gets translated to
Customers.Where( x=> x.Orders.Any( y=> y.Product.ProductID == 2))
There is no way to do this OData as of now.
Advantages of JSON
When you are using any JavaScript frameworks, creating query based on English syntax is little difficult, and composing query is difficult. But following method helps you in composing query easily as shown.
function query(name,phone,email){
var q = {};
if(name){
q["Name:StartsWith"] = name;
}
if(phone){
q["Phone:=="] = phone;
}
if(email){
q["Email:=="] = email;
}
return JSON.stringify(q);
}
Above method will compose query and "AND" everything if specified. Creating composable query is great advantage with JSON based query syntax.
in a dropdown I would like to find data in 2 levels. Maybe my logic is wrong, but as I remember I have done such things before, the only difference was that I got always 1 simple result back, but now, I should handle an array. Here's my code:
echo $form->dropDownList($model, 'szeriaGyartmanyId', GxHtml::listDataEx(
SzeriaGyartmany::model()->findAllAttributes(
null, true, 'rajz_osszetett_technologia_id IN (:rajz_osszetett_technologia_id) AND keszDb<db', array(
':rajz_osszetett_technologia_id' => RajzOsszetettTechnologia::model()->findAllAttributes(
null, true, 'osszetett_technologia_id = :osszetett_technologia_id', array(
':osszetett_technologia_id' => OsszetettTechnologia::model()->find("name='Horganyzás alatt'")->id
)
)->id
)
)
), array('style' => 'width: auto', 'prompt' => ''));
the core gives back one single ID, it's no problem, but the second level gives back an array (or array of objects? I'm not sure). The point is, is it possible here somehow to implode resulting rajz_osszetett_technologia_ids, or do I have to do completely differently? I've tried to implode it right in place, but I got an error: Argument must be an array. So that's why I guess the result is an array of objects.
Is it clear what I would like to achieve? For me it seems kinda obvious to do it somehow like this, but maybe my logic is completely wrong. Can somebody please point me to the right direction?
Thanks a lot!
BR
c
GxActiveRecord::findAllAttributes(null,true..) returns an array of objects with only the required properties set. In order to obtain an array of ids as required you need to wrap it in GxHtml::listDataEx() and then use array_keys to obtain only the keys.
echo $form->dropDownList($model, 'szeriaGyartmanyId', GxHtml::listDataEx(
....
':rajz_osszetett_technologia_id' => implode(',',
array_keys(
GxHtml::listDataEx(
RajzOsszetettTechnologia::model()->findAllAttributes(
....
)
)
)
)
....
)
Perhaps a custom query would be easier and clearer than this.
This is just a quick question on performance in an sql query using ruby and rails.
Basically I have a parent model and a bunch of children which have the variable of parent_ID.
I first gather all the parents with a specific condition and then I cycle through each parent finding any children that match.
Unfortunately this is incredibly slow and I was wondering if theres any help going in optimizing it.
#parents = Parent.where(:parent_id => 3) #This is passed in from params
#childrenArray =[]
#parents.each_with_index do |parent, index|
#TOOSLOW
#childrenArray[index] = Child.find(:all,:order=>"id",:conditions =>{:parent_ID=> parent.id})
end
One thing I thought is perhaps I should make an array of all the parent Ids to be searched and then do something like
child.find_by_parent_ID(myarrayofnumbershere)
However I don't know if this would be any better.
Any help or advice appreciated.
I'm very new to SQL and ruby. I'm aware a table joins would have been ideal here but I think I'm a bit late in my development to try it now. Also I need to serve up 2 seperate arrays. one of the parents and one of the children.
Try using the include method, like so:
#parents = Parent.where(:parent_id => 3).include(:children)
Now rails will have fetched the associated children and you should be able to loop over #parents and access their children without additional queries, like so:
#parents.each do |p|
puts "#{p}'s children: #{p.children}"
end
In rails 3, I would like to do the following:
SomeModel.where(:some_connection_id => anArrayOfIds).select("some_other_connection_id")
This works, but i get the following from the DB:
[{"some_other_connection_id":254},{"some_other_connection_id":315}]
Now, those id-s are the ones I need, but I am uncapable of making a query that only gives me the ids. I do not want to have to itterate over the resulst, only to get those numbers out. Are there any way for me to do this with something like :
SomeModel.where(:some_connection_id => anArrayOfIds).select("some_other_connection_id").values()
Or something of that nautre?
I have been trying with the ".select_values()" found at Git-hub, but it only returns "some_other_connection_id".
I am not an expert in rails, so this info might be helpful also:
The "SomeModel" is a connecting table, for a many-to-many relation in one of my other models. So, accually what I am trying to do is to, from the array of IDs, get all the entries from the other side of the connection. Basicly I have the source ids, and i want to get the data from the models with all the target ids. If there is a magic way of getting these without me having to do all the sql myself (with some help from active record) it would be really nice!
Thanks :)
Try pluck method
SomeModel.where(:some => condition).pluck("some_field")
it works like
SomeModel.where(:some => condition).select("some_field").map(&:some_field)
SomeModel.where(:some_connection_id => anArrayOfIds).select("some_other_connection_id").map &:some_other_connection_id
This is essentially a shorthand for:
results = SomeModel.where(:some_connection_id => anArrayOfIds).select("some_other_connection_id")
results.map {|row| row.some_other_connection_id}
Look at Array#map for details on map method.
Beware that there is no lazy loading here, as it iterates over the results, but it shouldn't be a problem, unless you want to add more constructs to you query or retrieve some associated objects(which should not be the case as you haven't got the ids for loading the associated objects).
Is there a way to clear old selects in a .select("table.col1, ...") statement?
Background:
I have a scope that requests accessible items for a given user id (simplified)
scope :accessible, lambda { |user_id|
joins(:users).select("items.*")
.where("items_users.user_id = ?) OR items.created_by = ?", user_id, user_id)
}
Then for example in the index action i only need the item id and title, so i would do this:
#items = Item.accessible(#auth.id).select("polls.id, polls.title")
However, this will select the columns "items., items.id, items.title". I'd like to avoid removing the select from the scope, since then i'd have to add a select("items.") everywhere else. Am I right to assume that there is no way to do this, and i either live with fetching too many fields or have to use multiple scopes?
Fortunately you're wrong :D, you can use the #except method to remove some parts of the query made by the relation, so if you want to remove the SELECT part just do :
#items = Item.accessible(#auth.id).except(:select).select("polls.id, polls.title")
reselect (Rails 6+)
Rails 6 introduced a new method called reselect, which does exactly what you need, it replaces previously set select statement.
So now, your query can be written even shorter:
#items = Item.accessible(#auth.id).reselect("polls.id, polls.title")