Updating Using Aggregate Function - sql

Question

I am trying to update a column of the table using the below query.. But I get an error
An aggregate may not appear in the set list of an UPDATE statement
Code:
UPDATE Test.dbo.Table1
SET InDate = MIN(b.Date)
FROM
Test.dbo.Table1 a
LEFT OUTER JOIN
Test.dbo.Table2 b
ON
a.ID1 = b.ID2
WHERE b.Code = 'IN';
I want to update the InDate column in my table with the oldest date from Table2 (b.Date) column where (b.code) is 'IN'
What is wrong in here?

Answer 1

You need to put the aggregate in a temp table or subquery and you need an explicit GROUP BY statement.
UPDATE Test.dbo.Table1
SET InDate = min_date
FROM Test.dbo.Table1 c inner join
(SELECT a.id1, MIN(b.Date) min_date
FROM Test.dbo.Table1 a
LEFT OUTER JOIN Test.dbo.Table2 b
ON a.ID1 = b.ID2
Group by a.id1) d
ON c.ID1 = d.ID1
WHERE c.Code = 'IN';

Answer 2

I think this will do what you want. I've removed the aliases to make it as clear as possible:
UPDATE Table1
SET InDate = (
SELECT MIN(Table2.Date)
FROM Table2
WHERE Table1.ID1 = Table2.ID2
AND Table2.Code = 'IN'
)

Answer 3

You could use apply to get the min date and then use that in the update statement:
UPDATE a
SET a.InDate = b.MinBDate
FROM Table1 a
OUTER APPLY
(
SELECT MIN(b.InDate) MinBDate
FROM Table2 b
WHERE b.Id = a.Id
AND b.Code = 'IN'
) b

Answer 4

Maybe this?
UPDATE Test.dbo.Table1
SET InDate = b.Date
FROM
Test.dbo.Table1 a
INNER JOIN (
select
b.ID2,
MIN(b.Date) Date
from Test.dbo.Table2 b
where
WHERE b.Code = 'IN'
group by
b.ID2
) b
ON
a.ID1 = b.ID2

Answer 5

Assuming your data model is something like the following, joining to a derived table should do the trick:
--Data Setup:
DECLARE #Table1 TABLE (ID1 INT, InDate DATETIME)
DECLARE #Table2 TABLE (ID2 INT, ID1 INT, Date DATETIME, Code VARCHAR(12))
INSERT INTO #Table1 (ID1)
VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10)
INSERT INTO #Table2 (ID2, ID1, Date, Code)
VALUES
(1, 1, '1/1/2014', 'OUT'),
(2, 1, '5/1/2014', 'IN'),
(3, 1, '3/1/2013', 'IN'),
(4, 2, '1/1/2014', 'OUT'),
(5, 2, '1/1/2014', 'IN'),
(6, 3, '1/1/2014', 'IN'),
(7, 4, '1/1/2014', 'IN'),
(8, 5, '1/1/2014', 'IN'),
(9, 6, '2/1/2014', 'OUT'),
(10, 7, '3/1/2014', 'IN'),
(11, 8, '4/1/2014', 'IN'),
(12, 9, '2/1/2014', 'IN'),
(12, 9, '2/1/2014', 'IN'),
(12, 10, '1/2/2014', 'IN'),
(12, 10, '1/3/2014', 'IN'),
(12, 10, '1/4/2014', 'IN'),
(12, 10, '1/1/2014', 'OUT')
--Actual Update:
UPDATE T1
SET InDate = T2.MinDate
FROM #Table1 T1
JOIN (SELECT T2.ID1, MIN(Date) AS MinDate
FROM #Table2 T2
WHERE T2.Code = 'IN'
GROUP BY T2.ID1) T2 ON T2.ID1 = T1.ID1
--Results
SELECT *
FROM #Table1