SELECT DISTINCT showing duplicate dates per customer email - sql-server

Question

I am trying to retrieve information for the past ten months, but am having a couple of errors. First, my query is getting data from as far back as 2013. Secondly, I am seeing duplicates in my results based on the PolEffDate field, like this:
EntityID | PolEffDate | EMail | CustNo | Producer | BusinessPhone
abcde-12345-fghij-67890 | 2013-09-24 | somewhere#email.com | 31000 | Bob Builder | 123-456-7890
abcde-12345-fghij-67890 | 2013-12-01 | somewhere#email.com | 31000 | Bob Builder | 123-456-7890
abcde-12345-fghij-67890 | 2014-09-24 | somewhere#email.com | 31000 | Bob Builder | 123-456-7890
Here is my SQL Query:
SELECT DISTINCT
CONVERT(VarChar(36), Customer.CustId) AS EntityID
, BasicPolInfo.PolEffDate, Customer.EMail, Customer.CustNo
, (isnull(Employee.Firstname + ' ','') + isnull(Employee.LastName,''))
AS Producer, Employee.BusFullPhone
FROM
Customer INNER JOIN BasicPolInfo ON Customer.CustId = BasicPolInfo.CustId INNER JOIN
Transaction ON BasicPolInfo.PolId = Transaction.PolId INNER JOIN
GeneralBranch ON Customer.GLBrnchCode = GeneralBranch.GLBrnchCode INNER JOIN
GeneralDepartment ON Customer.GLDeptCode = GeneralDepartment.GLDeptCode INNER JOIN
GeneralDivision ON Customer.GLDivCode = GeneralDivision.GLDivCode INNER JOIN
Employee ON BasicPolInfo.ExecCode = Employee.EmpCode
WHERE
BasicPolInfo.PolExpDate >= DATEADD(MONTH, -10,CONVERT(VARCHAR(11),GETDATE(),106))
AND BasicPolInfo.PolExpDate <= CONVERT(VARCHAR(11),GETDATE(),106)
AND Customer.Active = 'Y'
AND Customer.typeCust = 'P'
Thank you for the help. I will try my best to answer any questions.

Answer 1

Daniel, the duplication you are seeing is caused because you have multiple records in BasicPolInfo for each CustID value. You can confirm this by running the following query:
SELECT CustID, COUNT(*)
FROM BasicPolInfo
GROUP BY CustID
HAVING COUNT(*) > 1
Depending on your schema, this may not be an issue - after all, there is probably a perfectly legitimate reason for that! Multiple policies per Customer is my guess.
To resolve the duplication, I would recommend a GROUP BY with MIN() or MAX().
Your other issue, that of retrieving data from earlier dates, is because you are selecting the PolEffDate (presumably, policy effective date), but filtering the PolExpDate (presumably, policy expiration date). Which are you intending to use? Policies that have finished sometime in the last ten months could have started much earlier than that.
To resolve the wider date range, reference the same value in your SELECT and WHERE clauses.
Query below (using MAX() and PolExpDate):
SELECT
CONVERT(VarChar(36), Customer.CustId) AS EntityID,
MAX(BasicPolInfo.PolExpDate) AS PolExpDate, -- note that this is now PolExpDate
Customer.EMail,
Customer.CustNo,
(isnull(Employee.Firstname + ' ','') + isnull(Employee.LastName,'')) AS Producer,
Employee.BusFullPhone
FROM
Customer INNER JOIN
BasicPolInfo ON Customer.CustId = BasicPolInfo.CustId INNER JOIN
[Transaction] ON BasicPolInfo.PolId = [Transaction].PolId INNER JOIN
GeneralBranch ON Customer.GLBrnchCode = GeneralBranch.GLBrnchCode INNER JOIN
GeneralDepartment ON Customer.GLDeptCode = GeneralDepartment.GLDeptCode INNER JOIN
GeneralDivision ON Customer.GLDivCode = GeneralDivision.GLDivCode INNER JOIN
Employee ON BasicPolInfo.ExecCode = Employee.EmpCode
WHERE
BasicPolInfo.PolExpDate >= DATEADD(MONTH, -10,CONVERT(VARCHAR(11),GETDATE(),106))
AND BasicPolInfo.PolExpDate <= CONVERT(VARCHAR(11),GETDATE(),106)
AND Customer.Active = 'Y'
AND Customer.typeCust = 'P'
GROUP BY
CONVERT(VarChar(36), Customer.CustId),
Customer.EMail,
Customer.CustNo,
(isnull(Employee.Firstname + ' ','') + isnull(Employee.LastName,'')),
Employee.BusFullPhone