Большинство дополнительных методов LINQ возвращает результаты. ForEach не вписывается в этот шаблон, поскольку это ничего не возвращает.
There is no way to do it in a DB-agnostic way. So you need to get the whole data-set like this:
select
r.name as ResName,
a.name as AppName
from
Resouces as r,
Applications as a,
ApplicationsResources as ar
where
ar.app_id = a.id
and ar.resource_id = r.id
And then concat the AppName programmatically while grouping by ResName.
Using COALESCE to Build Comma-Delimited String in SQL Server
http://www.sqlteam.com/article/using-coalesce-to-build-comma-delimited-string
Example:
DECLARE @EmployeeList varchar(100)
SELECT @EmployeeList = COALESCE(@EmployeeList + ', ', '') +
CAST(Emp_UniqueID AS varchar(5))
FROM SalesCallsEmployees
WHERE SalCal_UniqueID = 1
SELECT @EmployeeList
SELECT r.name,
GROUP_CONCAT(a.name SEPARATOR ',')
FROM RESOURCES r
JOIN APPLICATIONSRESOURCES ar ON ar.resource_id = r.id
JOIN APPLICATIONS a ON a.id = ar.app_id
GROUP BY r.name
SELECT r.name,
STUFF((SELECT ','+ a.name
FROM APPLICATIONS a
JOIN APPLICATIONRESOURCES ar ON ar.app_id = a.id
WHERE ar.resource_id = r.id
GROUP BY a.name
FOR XML PATH(''), TYPE).value('.','VARCHAR(max)'), 1, 1, '')
FROM RESOURCES r
SELECT r.name,
STRING_AGG(a.name, ',')
FROM RESOURCES r
JOIN APPLICATIONSRESOURCES ar ON ar.resource_id = r.id
JOIN APPLICATIONS a ON a.id = ar.app_id
GROUP BY r.name
I recommend reading about string aggregation/concatentation in Oracle.
To be agnostic, drop back and punt.
Select a.name as a_name, r.name as r_name
from ApplicationsResource ar, Applications a, Resources r
where a.id = ar.app_id
and r.id = ar.resource_id
order by r.name, a.name;
Now user your server programming language to concatenate a_names while r_name is the same as the last time.
I don't know if there's any solution to do this in a database-agnostic way, since you most likely will need some form of string manipulation, and those are typically different between vendors.
For SQL Server 2005 and up, you could use:
SELECT
r.ID, r.Name,
Resources = STUFF(
(SELECT ','+a.Name
FROM dbo.Applications a
INNER JOIN dbo.ApplicationsResources ar ON ar.app_id = a.id
WHERE ar.resource_id = r.id
FOR XML PATH('')), 1, 1, '')
FROM
dbo.Resources r
It uses the SQL Server 2005 FOR XML PATH
construct to list the subitems (the applications for a given resource) as a comma-separated list.
Marc
Это сделает это в SQL Server:
DECLARE @listStr VARCHAR(MAX)
SELECT @listStr = COALESCE(@listStr+',' ,'') + Convert(nvarchar(8),DepartmentId)
FROM Table
SELECT @listStr
Предполагая, что SQL Server:
Структура таблицы:
CREATE TABLE [dbo].[item_dept](
[ItemName] char(20) NULL,
[DepartmentID] int NULL
)
Запрос:
SELECT ItemName,
STUFF((SELECT ',' + rtrim(convert(char(10),DepartmentID))
FROM item_dept b
WHERE a.ItemName = b.ItemName
FOR XML PATH('')),1,1,'') DepartmentID
FROM item_dept a
GROUP BY ItemName
Результаты:
ItemName DepartmentID
item1 21,13,9,36
item2 4,9,44
Я полагаю, что вы хотите:
SELECT ItemName, GROUP_CONCAT(DepartmentId) FROM table_name GROUP BY ItemName
Если вы используете MySQL
Reference
Начиная с следующей версии SQL Server вы сможете делать
SELECT r.name,
STRING_AGG(a.name, ',')
FROM RESOURCES r
JOIN APPLICATIONSRESOURCES ar
ON ar.resource_id = r.id
JOIN APPLICATIONS a
ON a.id = ar.app_id
GROUP BY r.name
Для предыдущих версий продукта существует множество различных подходов к этой проблеме. Отличный обзор их можно найти в статье: Объединение значений строк в Transact-SQL .
Объединение значений, когда количество элементов неизвестно
Ненадежные подходы