I am struggling with converting multi-rows values which are belong to the same user into collection.
Here is a simple scenario.
users Table:userid, password
address Table:address, userid
Users Table and Address Table are one-to-many related--one user might have multi-addresses.
Assume the User's ID is 1001 while he/she have two addresses one is in Auckland and another one is Wellington.
I would like select both of them together with user's id.
1001 Auckland
1001 Wellington
So the question is are there any approach is able to put these two value into collection like list.
public class UserDetails{
private List<String> _Address
public string userid{get;set;}
public List<String> Address{
get{retrun _Address;}
set{_Address=value;}
}
}
var user_address= from _user in users
join _address in address on _user.userid=_address.userid
select new userDetails{
userid=_user.userid
**Address.add()**
};
Does anyone know how to construct the List in the LINQ and call the add method.
I want to put the list object into one row so that avoid the redundancy of userid.
Thanks for your help.
Maybe something like this:
var user_address= from _user in users
select new userDetails{
userid=_user.userid,
Address=(from _address in address
where _user.userid=_address.userid
select _address.:address
).ToList()
};
You do not have to join the address table.
Related
Imagine we have the following models:
type Company struct {
gorm.Model
Name string
Addresses []Address
}
type Address struct {
gorm.Model
CompanyID uint64
Street string
City string
Country string
}
I want to take all the companies(and their addresses) which have address in a specific location. Something like this:
SELECT company.*, address.* FROM company
INNER JOIN address ON address.company_id = company.id AND address.country = 'Bulgaria'
So if a company does not have address at the specific location, I will not get it as a result at all. I was trying something like that:
db.Joins("Addresses", "addresses.country = ?", "Bulgaria").Find(&companies)
However, it doesn't work, because GORM doesn't take the second argument of Joins(when preloading join used), so I should check the generated query and make something like that:
db.Where(`"Address".country = ?`, "Bulgaria").Joins("Addresses").Find(&companies)
Is there a better way/not hacky way? Have in mind all of the above code is mock of the real problem, I didn't want to expose the original models/queries.
You can use Preload to load Addresses into the Company object.
Based on your described conditions, where you don't want to load companies that don't match your filter, you should use an INNER JOIN
Two options:
First, if your table is named company, then your query should look like this:
db.Table("company").
Preload("Addresses").
Joins("INNER JOIN addresses a ON a.company_id = company.id").
Where("a.country = ?", "Bulgaria").
Find(&companies)
Second, if your table is named companies, then you should try this:
db.Preload("Addresses").
Joins("INNER JOIN addresses a ON a.company_id = companies.id").
Where("a.country = ?", "Bulgaria").
Find(&companies)
If you are using Gorm v2 you perform CRUD operations on has-one and one-to-many via associations:
var companies []Company
var addresses []Address
countries := []string{"Bulgaria"}
db.Model(&Address).Where("country IN (?)", countries).Find(&addresses)
// The key is using the previously fetched variable as the model for the association query
db.Model(&addresses).Association("CompanyID").Find(&companies)
This also works for many-to-many relations.
When comparing Gorm VS raw SQL queries (db.Raw(SQLquery)) you will typically see a performance hit. On the upside, you will not have to deal with the added complexity of raw sql string building in Go, which is pretty nice. I personally use a combination of both raw and gorm-built queries in my projects :)
I have three tables - Chairman, Designation, Members.
MY requirement is to map the member to chairman and assign member a role.
I was able to fetch the list of members under the chairman when I had chairman_id and designation_id in the members table.
Since the chairman change, most of the members stay intact. So I came up with an idea of indexing them
Table - membermap
id | chairman_id | designation_id | member_id
So the list is preserved how many chairmans come and go. I dont need to create new profile for new chairman rather than map to it.
I am now sure how do I do it,
So far I was able to pull the ID but I am not sure how do I join the tables
Tables
Chairman
id| name
Designation
id|designation
Members
id|members
Here is my controller
$mapmember = Statechairman::findOrFail($id)->statechairmembersmap;
dd($mapmember);
In this Iam getting the statechairmembersmap but it's fetching all the result and not limiting the match.
I also tried to join the query using the DB
$mapmember = DB::table('statechairmen')
->join('state_chairman_members_maps', 'state_chairman_members_maps.chairman_id','statechairmen.id')
->join('statemembers','statemembers.id','state_chairman_members_maps.members_id')
->select('state_chairman_members_maps.*')->get();
but this result show me the Table - membermap but not the other results.
My Models:
Chairman :
public function statechairmembersmap(){
return $this->hasMany('App\StateChairmanMembersMap','chairman_id','id');
}
public function statemembers(){
return $this->hasMany('App\Statemembers','chairman_id', 'id');
}
public function statedesignation(){
return $this->hasMany('App\Statedesignation','id','designation_id');
}
membermap:
protected $table = 'state_chairman_members_maps';
protected $dates = ['deleted_at'];
public function statechairman(){
return $this->belongsTo('App\Statechairman','id');
}
public function statedesignations(){
return $this->belongsTo('App\Statedesignation','designation_id','id');
}
public function statemembers(){
return $this->belongsTo('App\Statemembers','members_id','id');
}
Please assist me where I doing wrong.
Thanks a lot for checking the question out.
Finally after a lot of strugle, I was able to find it by myself.
$mapmembers = DB::table('state_chairman_members_maps')
->join('statechairmen','statechairmen.id','=','state_chairman_members_maps.chairman_id')
->join('statemembers','statemembers.id','=','state_chairman_members_maps.members_id')
->join('statedesignations','statedesignations.id','=','state_chairman_members_maps.designation_id')
->where('chairman_id','=',$id)
->get();
Here is what I came up with.
Here I have joined 3 tables and mapped the id comming from the chairman to filter the result. I getting the results.
I have two tables: users (Users) and groups (Groups).
Users
-----------------
id | username | group
1 | Bob | 2
Groups
-----------------
id | name
1 | firstgroup
2 | secondgroup
I would like to display: users.ID, users.username, group.name (1, Bob, secondgroup)
An SQL statement like so would work:
SELECT Users.id, Users.username, Groups.name
FROM Users
INNER JOIN
Groups ON Groups.id = Users.group
However, I'm struggling to write this in Eloquent, since there is no "FROM". At the moment I'm going for something along the lines of the below, using JOINS (http://laravel.com/docs/queries#joins)
$users = Users::select('id','username', 'Groups.name')->joins('Groups.id', '=', 'id')->get();
Now this isn't working - I think the joins has to come before the select but I just can't work it out :(
I think you're confusing a few things here...
You're mixing Eloquent with the lower-level DB::table('foo')->select() syntax. When you want to use Eloquent I suggest you take a look at the docs about relationships in Eloquent.
You should define your models like so:
class User extends Eloquent {
public function group()
{
return $this->belongsTo('Group', 'group');
// second parameter is necessary because you didnt
// name the column "group_id" but simply "group"
}
}
class Group extends Eloquent {
public function users()
{
return $this->hasMany('User', 'group');
}
}
This sets up all the joins you might be needing later. You can then simply use User::with('group')->all(); and have the query built and run for you.
Database: Query Builder(DB) is not a Eloquent(ORM):
Database query builder you have to inform the table names and the fields, like it says on in your related link of laravel docs: "...provides a convenient, fluent interface to creating and running database queries." like these query below:
$users = DB::table('users')
->join('contacts', 'users.id', '=', 'contacts.user_id')
->join('orders', 'users.id', '=', 'orders.user_id')
->select('users.*', 'contacts.phone', 'orders.price')
->get();
Eloquent is a ORM - Object related Mapping, it means that your class User is related to the table users (look at you files Migrations) and this class extends the Model Class, thus you can access the methods like these bellow:
class User extends Models
{
public static function usersWithGroups(){
return User::select('id', 'name', 'email')->with('groups')->get();
}
}
Observe that method is into the class User, so you can access that in a static way "User::", using Eloquent you'll have many hidden static methods that will improve you time codding, because you are inheriting de Model methods, to more details visit the Eloquent Docs at: Eloquent Docs
I have a Linq-to-Entities query that is not complicated but requires an .include and/or projection and/or join because it must be executed in one pass.
Here is my database (Microsoft SQL Server 2008):
Table A (Customers) (contains CustomerID (customer IDs), and ZipCode (zip codes) as strings.
Table C (Categories) (contains CategoryID (categories) like "food", "shelter","clothing", "housing" (primary keys).
Table A_C is a linking table, since Tables A and C are linked as many-to-many: contains just two fields: CustomerID "customer IDs" and CategoryID (Categories), in combination as primary keys. This table is a linking table betweeen tables A and C.
Here is my query, that must be executed in just one trip to the database: I need to select all records in Table A that satisfy a condition, then filter these records depending on a 'list of parameters' that are found in the linking Table A_C--and do this all in one trip to the database. But I don't know what the length or composition of the list of parameters for Table A_C is, ahead of time--it varies from call to call. Thus this list of parameters varies method call by method call.
To give a more concrete example:
Table A has a list of customer IDs. I find the customers that live in a certain Zip code. Then, in the same SQL query, I need to find which of these customers have selected certain categories: Food, Clothing, Housing, etc, but my web method does not know ahead of time what these categories are, rather, they are passed as a list to the method: List myCategoryList (which could be 1 category or 100 categories, and varies method call by method call).
How do I write the projection using Linq-to-Entities? When the list of parameters varies? And do it all in one pass?
List<string> CategoryList = new List<string>() { "Food", "Shelter", "Housing" }; // in one call to the web service method
List<string> CategoryList = new List<string>() { "Food", "Clothing" }; //could be a second call--it varies and I don't know ahead of time what the List will be
So how can I do the SQL query using Linq-to-Entities? In one pass? (Of course I could loop through the list, and make repeated trips to the database, but that's not an optimal solution I am told). Projection,.Include are keywords but surfing the net yielded nothing.
Here is a crude guess, just to get ball rolling:
public void WebMethod1 (CategoryList)
{
using (EntityFramework1 context = new EntityFramework1())
{
/* assume CategoryList is a list of strings passed into the method and is,for this particular call,something like: List<string> CategoryList = new List<string>() { "Food", "Clothing" }; for this call, but in the next call it could be: List<string> CategoryList = new List<string>() { "Food", "Shelter", "Housing" } */
string ZipCodeString = "12345";
string customerIDString = "E12RJ55";
var CustomersFromZipCodeHavingSelectedCertainCategories = from x in context.A_C
where x.A.CustomerID == customerIDString
where x.A.StartsWith(ZipCodeString)
where x.A_C.Contains(CategoryList) //???? This is clearly not grammatical, but what is?
select x;
}
/*
my problem is: I want to filter all records from A that contain a zipcode 12345, and that also have a certain CustomerID "E12RJ55" from table A, but further filter this set with all such CustomerIDs in linking table A_C that contain the categories "Food" and "Clothing".
How to do this in one pass? I can do this quite easily in multiple passes and trips to the database using code, but somebody in this thread here http://bit.ly/rEG2AM suggested I do a Join/projection and do it all in one fell swoop.
*/
I will also accept SQL answers since it might help yield a solution. This question btw is not difficult I believe--but I could not find an answer on the net.
EDIT: with answer and credit to david s.
I thank you for the answer david.s. Here is what worked, slightly different than the answer by david.s, in that I am using the linking table (bridge table) called “Customer_Categories” that is between the table Customer and Categories and contains the primary key of each (as is required for many-to-many relationships). This bridge table is what I called "A_C" in my original answer, and here has ints rather than strings but is the same thing. Intellisense picked up this table and I used it, and it works. Also keep in mind that CategoryList is a list of ints, List CategoryList = new List();, yet amazingly it automagically works inside this SQL-to-Entities query:
Var CustomersFromZipCOde = context.Customers.Where (custo => custo.CustomerID==customerIDString && custo.ZipCode.StartsWith(ZipCodeString) && custo.Customer_Categories.Any(categ => CategoryList.Contains(categ.CategoryID)));
//gives the right output, incredible.
First of all i would like to say that even if you explanation is very long it is not very clear. You would like a simple Linq-to-Entities query but you don't give the Entities, you only speak of tables in your database.
Assuming you have the following entities:
public class Customer
{
public string CustomerID { get; set; }
public string ZipCode { get; set; }
public virtual ICollection<Category> Categories { get; set; }
}
public class Category
{
public string CategoryID { get; set; }
public virtual ICollection<Customer> Customers { get; set; }
}
Your query might look like this:
var CustomersFromZipCodeHavingSelectedCertainCategories =
context.Customers.Where(
customer => customer.CustomerID == customerIDString &&
customer.ZipCode.StartsWith(ZipCodeString) &&
customer.Categories.Any(
category => CategoryList.Contains(category.CategoryID));
More info on other ways to do this here:
http://smehrozalam.wordpress.com/2010/06/29/entity-framework-queries-involving-many-to-many-relationship-tables/
I have two entities, Location and Industry, and a link-table between them. I've configured a many-to-many relationship, in both directions, between the two entities.
In a search query, I'm trying to select Locations that are associated with a list of industries.
After days and days of trying to wrangle the criteria API, I've decided to drop down to HQL and abandon the criteria API. But even that isn't going well for me - it seems, regardless of whether I hand-write this HQL query, or let the criteria API do it, I end up with the same result.
I managed to produce the right result in two ways - like this:
var q = Data.Query("select distinct loc from Location loc join loc.Industries ind where ind in (:ind)");
q.SetParameterList("ind", new Industry[] { Data.GetIndustry(4), Data.GetIndustry(5) });
And (better) like that:
var q = Data.Query("select distinct loc from Location loc join loc.Industries ind where ind.id in (:ind)");
q.SetParameterList("ind", new int[] { 4, 5 });
Unfortunately, both result in a sub-optimal query:
select distinct
location0_.Id as Id16_,
location0_.Name as Name16_,
(etc.)
from Location location0_
inner join LocationIndustry industries1_
on location0_.Id=industries1_.LocationId
inner join Industry industry2_
on industries1_.IndustryId=industry2_.Id
where
industry2_.Id in (? , ?)
Why the extra join?
Is NH not smart enough to know that the Industry.Id property, being the only Industry-property involved in the query, is stored in the LocationIndustry link-table, and there is no need for the extra join to the Industry table itself?
Or am I doing something wrong?
Ideally, the most intuitive thing for me would be to write:
from Location loc where loc.Industries in (:ind)
This does not work - it throws an error and says it does not know about the Industries property. I guess because Industries, being a "property" in programming terms, is actually a "relationship" in terms of DBMS.
What is the simplest and most efficient way to write this query in HQL?
Thanks!
I'm not sure you can avoid this extra join given the mapping strategy you have used.
You could avoid it by using an intermediary class but this would mean you would need a class structure like this:
public class Industry {
//Other stuff
public virtual List<LocationIndustry> LocationIndustries {get; set:;}
}
public class LocationIndustry {
public virtual Location Location {get; set;}
public virtual Industry Industry {get; set;}
}
public class Location {
//normal stuff
public virtual IList<LocationIndustry> LocationIndustries {get; set;}
}
Then you can query on the LocationIndustry class and avoid the join to Location.