Update a Table Based on Count from Another Table - sql-server

Question

I am trying to do a COUNT against a table using a date range, from another table. The count has to also match with a reference number, here's the data format:
[Rev Old New] (Table 1)
Id Start Finish Amount Calls
41 2018-01-01 2018-06-01 111.01
[Calls] (Table 2)
Id Date Amount
3 2018-05-05 12.1
41 2018-01-03 11.7
41 2018-06-11 12.9
I am quite new to MS SQL so apologies for my rather basic knowledge!
So, I want the count of rows in [Calls], where the Date is between the Start and Finish dates in [Rev Old New] and the ID is the same in both tables (it's a client ref)
I want to UPDATE [Rev Old New] with this value in [Calls]
Here's what I have so far, not working and probably nowhere near the right syntax!
UPDATE [Insight].[dbo].[Rev Old New]. t2
SET [Calls] =
(SELECT COUNT(CASE WHERE t1.Date BETWEEN t2.[Start] AND t2.[Finish])
FROM [Insight].[dbo].[Calls] t1
WHERE t1.[Id] = t2.[Id])
The error I get is this:
Msg 102, Level 15, State 1, Line 1
Incorrect syntax near 't2'.
Msg 156, Level 15, State 1, Line 3
Incorrect syntax near the keyword 'WHERE'.

Answer 1

You don't need the CASE statement, a simple WHERE will suffice:
UPDATE [Insight].[dbo].[Rev Old New]
SET [Rev Old New].[Calls] = (SELECT COUNT(*) FROM [Insight].[dbo].[Calls] t1
WHERE t1.Date BETWEEN [Rev Old New].[Start] AND [Rev Old New].[Finish])

Answer 2

this may help
CREATE TABLE #RevOldNew(Id BIGINT, Start DATETIME, Finish DATETIME, Amount BIGINT, Calls INT)
CREATE TABLE #Calls(Id BIGINT,[Date] DATETIME, AMOUNT BIGINT)
INSERT INTO #RevOldNew
SELECT 1,'2018-06-01','2018-06-15',NULL,NULL UNION ALL
SELECT 1,'2018-07-16','2018-07-31',NULL,NULL UNION ALL
SELECT 1,'2018-08-01','2018-08-15',NULL,NULL UNION ALL
SELECT 1,'2018-08-16','2018-08-31',NULL,NULL UNION ALL
SELECT 2,'2018-07-01','2018-07-15',NULL,NULL UNION ALL
SELECT 2,'2018-08-01','2018-08-15',NULL,NULL UNION ALL
SELECT 2,'2018-08-16','2018-08-31',NULL,NULL UNION ALL
SELECT 3,'2018-07-16','2018-07-31',NULL,NULL UNION ALL
SELECT 3,'2018-08-01','2018-08-15',NULL,NULL UNION ALL
SELECT 3,'2018-08-16','2018-08-31',NULL,NULL
INSERT INTO #Calls
SELECT 1,'2018-07-16',23 UNION ALL
SELECT 1,'2018-07-21',534 UNION ALL
SELECT 1,'2018-07-28',456 UNION ALL
SELECT 1,'2018-08-02',43 UNION ALL
SELECT 1,'2018-08-11',565 UNION ALL
SELECT 1,'2018-08-20',56 UNION ALL
SELECT 2,'2018-07-05',576 UNION ALL
SELECT 2,'2018-08-22',54 UNION ALL
SELECT 2,'2018-08-29',676 UNION ALL
SELECT 3,'2018-07-17',32 UNION ALL
SELECT 3,'2018-08-15',43
;with cte
As (
SELECT r.id,r.Start,r.Finish, SUM(c.AMOUNT) Amount, COUNT(c.id) calls
FROM #RevOldNew r
LEFT JOIN #Calls c on r.id=c.id and c.Date between r.Start and r.Finish
Group by r.id,r.Start,r.Finish
)
UPDATE r
SET r.Amount=c.Amount,
r.Calls=c.calls
FROM #RevOldNew r
JOIN cte c on c.id=r.id and c.Start=r.Start and c.Finish=r.Finish
SELECT * from #RevOldNew
DROP TABLE #RevOldNew
DROP TABLE #Calls

Answer 3

First you should avoid spaces in table names. It's not a good practice.
Then a query which solves your problem is :
update [Rev Old New]
set Calls=(select count(*) from Calls where [Rev Old New].id = Calls.id and Calls.date >= [Rev Old New].Start and Calls.date <= [Rev Old New].Finish)
where
select count(*) from Calls where [Rev Old New].id = Calls.id and Calls.date >= [Rev Old New].Start and Calls.date <= [Rev Old New].Finish
count the lines from Calls with the id in [Rev Old New] with date in Calls between Finish and Start (included) in [Rev Old New]
I hope this helps.