How to use aggregate in the set list of an UPDATE statement - sql

Question

Let me describe the whole situation: I have below two tables. The values of MaxTestCasesExecutedBySingleUser and TotalTestCasesExecutedByAllUser in Module table needs to be updated using some Aggregate clause
CREATE TABLE [dbo].[Module](
[ProjectID] [int] NOT NULL,
[ModuleID] [int] NOT NULL,
[ModuleName] [nvarchar](100) NOT NULL,
[MaxTestCasesExecutedBySingleUser] [int] NULL,
[TotalTestCasesExecutedByAllUser] [int] NULL,
PRIMARY KEY ([ProjectID],[ModuleID]))
CREATE TABLE [dbo].[ModuleMember](
[ProjectID] [int] NOT NULL,
[ModuleID] [int] NOT NULL,
[SerialNo] [int] NOT NULL,
[Name] [nvarchar](100) NOT NULL,
PRIMARY KEY ([ProjectID],[ModuleID],[SerialNo]))
Insert Into Module Values (1,1,'Installation_Test',null,null)
Insert Into Module Values (1,2,'Server_Test',null,null)
Insert Into Module Values (1,3,'Client_Test',null,null)
Insert Into Module Values (1,4,'Security_Test',null,null)
Insert Into ModuleMember Values(1,1,0,'Jim')
Insert Into ModuleMember Values(1,1,1,'Bob')
Insert Into ModuleMember Values(1,2,0,'Jack')
Insert Into ModuleMember Values(1,2,1,'Steve')
Insert Into ModuleMember Values(1,2,2,'Roy')
Insert Into ModuleMember Values(1,2,3,'Jerry')
Insert Into ModuleMember Values(1,3,0,'Root')
Insert Into ModuleMember Values(1,3,1,'Tom')
Insert Into ModuleMember Values(1,4,0,'Evil')
There is another Table Valued Function dbo.GetValue which takes Name (from ModuleMember table) as parameter and returns the values of Name and TestCasesExecutedByTheUser in the form of a table. I need to update these two values in Module table.
Definition:
MaxTestCasesExecutedBySingleUser = maximum number if test case executed by a member in a module
TotalTestCasesExecutedByAllUser = total number of test cases executed by all member in a module.
I tried below query but it is throwing me error : An aggregate may not appear in the set list of an UPDATE statement.
UPDATE M
SET
M.MaxTestCasesExecutedBySingleUser = MAX(N.TestCasesExecutedByTheUser),
M.TotalTestCasesExecutedByAllUser = SUM(N.TestCasesExecutedByTheUser)
FROM Module M
JOIN ModuleMember Mem ON (M.ProjectID = Mem.ProjectID AND M.ModuleID = Mem.ModuleID)
CROSS APPLY dbo.GetValue(Mem.Name) N

Answer 1

The workaround is a little more verbose - you have to get the aggregates first (e.g. in a CTE), and then update the target table:
;WITH src AS
(
SELECT
Mem.ProjectID,
Mem.ModuleID,
mtc = MAX(N.TestCasesExecutedByTheUser),
stc = SUM(N.TestCasesExecutedByTheUser)
FROM dbo.ModuleMember AS Mem
CROSS APPLY dbo.GetValue(Mem.Name) AS N
GROUP BY Mem.ProjectID, Mem.ModuleID
)
UPDATE M
SET M.MaxTestCasesExecutedBySingleUser = src.mtc,
M.TotalTestCasesExecutedBySingleUser = src.stc
FROM dbo.Module AS M
INNER JOIN src
ON M.ProjectID = src.ProjectID
AND M.ModuleID = src.ModuleID;

Answer 2

I think it's perfect case to use apply
update Module set
MaxTestCasesExecutedBySingleUser = C.maxtc,
TotalTestCasesExecutedByAllUser = C.sumtc
from Module as M
cross apply (
select
max(N.TestCasesExecutedByTheUser) as maxtc,
sum(N.TestCasesExecutedByTheUser) as sumtc
from ModuleMember as MM
cross apply dbo.GetValue(MM.Name) as N
where MM.ProjectID = M.ProjectID and MM.ModuleID = M.ModuleID
) as C