select all records from one table and return null values where they do not have another record in second table - sql

Question

I have looked high and low for this particular query and have not seen it.
We have two tables; Accounts table and then Visit table. I want to return the complete list of account names and fill in the corresponding fields with either null or the correct year etc. this data is used in a matrix report in SSRS.
sample:
Acounts:
AccountName AccountGroup Location
Brown Jug Brown Group Auckland
Top Shop Top Group Wellington
Super Shop Super Group Christchurch
Visit:
AcccountName VisitDate VisitAction
Brown Jug 12/12/2012 complete
Super Shop 1/10/2012 complete
I need to select weekly visits and show those that have had a complete visit and then the accounts that did not have a visit.
e.g.
Year Week AccountName VisitStatus for week 10/12/2012 should show
2012 50 Brown Jug complete
2012 50 Top Group not complete
2012 50 Super Shop not complete
e.g.
Year Week AccountName VisitStatus for week 1/10/2012 should show
2012 2 Brown Jug not complete
2012 2 Top Group not complete
2012 2 Super Shop complete

Answer 1

please correct me if am worng
select to_char(v.visitdate,'YYYY') year,
to_char(v.visitdate,'WW') WEAK,a.accountname,v.visitaction
from accounts a,visit v
where a.accountname=v.ACCCOUNTNAME
and to_char(v.visitdate,'WW')=to_char(sysdate,'WW')
union all
select to_char(sysdate,'YYYY') year,
to_char(sysdate,'WW') WEAK,a.accountname,'In Complete'
from accounts a
where a.accountname not in ( select v.ACCCOUNTNAME
from visit v where to_char(v.visitdate,'WW')=to_char(sysdate,'WW'));

Answer 2

The following answer assumes that
A) You want to see every week within a given range, whether any accounts were visited in that week or not.
B) You want to see all accounts for each week
C) For accounts that were visited in a given week, show their actual VisitAction.
D) For accounts that were NOT visited in a given week, show "not completed" as the VisitAction.
If all those are the case then the following query may do what you need. There is a functioning sqlfiddle example that you can play with here: http://sqlfiddle.com/#!3/4aac0/7
--First, get all the dates in the current year.
--This uses a Recursive CTE to generate a date
--for each week between a start date and an end date
--In SSRS you could create report parameters to replace
--these values.
WITH WeekDates AS
(
SELECT CAST('1/1/2012' AS DateTime) AS WeekDate
UNION ALL
SELECT DATEADD(WEEK,1,WeekDate) AS WeekDate
FROM WeekDates
WHERE DATEADD(WEEK,1,WeekDate) <= CAST('12/31/2012' AS DateTime)
),
--Next, add meta data to the weeks from above.
--Get the WeekYear and WeekNumber for each week.
--Note, you could skip this as a separate query
--and just included these in the next query,
--I've included it this way for clarity
Weeks AS
(
SELECT
WeekDate,
DATEPART(Year,WeekDate) AS WeekYear,
DATEPART(WEEK,WeekDate) AS WeekNumber
FROM WeekDates
),
--Cross join the weeks data from above with the
--Accounts table. This will make sure that we
--get a row for each account for each week.
--Be aware, this will be a large result set
--if there are a lot of weeks & accounts (weeks * account)
AccountWeeks AS
(
SELECT
*
FROM Weeks AS W
CROSS JOIN Accounts AS A
)
--Finally LEFT JOIN the AccountWeek data from above
--to the Visits table. This will ensure that we
--see each account/week, and we'll get nulls for
--the visit data for any accounts that were not visited
--in a given week.
SELECT
A.WeekYear,
A.WeekNumber,
A.AccountName,
A.AccountGroup,
IsNull(V.VisitAction,'not complete') AS VisitAction
FROM AccountWeeks AS A
LEFT JOIN Visits AS V
ON A.AccountName = V.AccountName
AND A.WeekNumber = DATEPART(WEEK,V.VisitDate)
--Set the maxrecursion number to a number
--larger than the number of weeks you will return
OPTION (MAXRECURSION 200);
I hope that helps.