T-SQL - Finding records with chronological gaps - sql-server

Question

This is my first post here. I'm still a novice SQL user at this point though I've been using it for several years now. I am trying to find a solution to the following problem and am looking for some advice, as simple as possible, please.
I have this 'recordTable' with the following columns related to transactions; 'personID', 'recordID', 'item', 'txDate' and 'daySupply'. The recordID is the primary key. Almost every personID should have many distinct recordID's with distinct txDate's.
My focus is on one particular 'item' for all of 2017. It's expected that once the item daySupply has elapsed for a recordID that we would see a newer recordID for that person with a more recent txDate somewhere between five days before and five days after the end of the daySupply.
What I'm trying to uncover are the number of distinct recordID's where there wasn't an expected new recordID during this ten day window. I think this is probably very simple to solve but I am having a lot of difficulty trying to create a query for it, let alone explain it to someone.
My thought thus far is to create two temp tables. The first temp table stores all of the records associated with the desired items and I'm just storing the personID, recordID and txDate columns. The second temp table has the personID, recordID and the two derived columns from the txDate and daySupply; these would represent the five days before and five days after.
I am trying to find some way to determine the number of recordID's from the first table that don't have expected refills for that personID in the second. I thought a simple EXCEPT would do this but I don't think there's anyway of getting around a recursive type statement to answer this and I have never gotten comfortable with recursive queries.
I searched Stackoverflow and elsewhere but couldn't come up with an answer to this one. I would really appreciate some help from some more clever data folks. Here is the code so far. Thanks everyone!
CREATE TABLE #temp1 (personID VARCHAR(20), recordID VARCHAR(10), txDate
DATE)
CREATE TABLE #temp2 (personID VARCHAR(20), recordID VARCHAR(10), startDate
DATE, endDate DATE)
INSERT INTO #temp1
SELECT [personID], [recordID], txDate
FROM recordTable
WHERE item = 'desiredItem'
AND txDate > '12/31/16'
AND txDate < '1/1/18';
INSERT INTO #temp2
SELECT [personID], [recordID], (txDate + (daySupply - 5)), (txDate +
(daySupply + 5))
FROM recordTable
WHERE item = 'desiredItem'
AND txDate > '12/31/16'
AND txDate < '1/1/18';

Answer 1

I agree with mypetlion that you could have been more concise with your question, but I think I can figure out what you are asking.
SQL Window Functions to the rescue!
Here's the basic idea...
CREATE TABLE #fills(
personid INT,
recordid INT,
item NVARCHAR(MAX),
filldate DATE,
dayssupply INT
);
INSERT #fills
VALUES (1, 1, 'item', '1/1/2018', 30),
(1, 2, 'item', '2/1/2018', 30),
(1, 3, 'item', '3/1/2018', 30),
(1, 4, 'item', '5/1/2018', 30),
(1, 5, 'item', '6/1/2018', 30)
;
SELECT *,
ABS(
DATEDIFF(
DAY,
LAG(DATEADD(DAY, dayssupply, filldate)) OVER (PARTITION BY personid, item ORDER BY filldate),
filldate
)
) AS gap
FROM #fills
ORDER BY filldate;
... outputs ...
+----------+----------+------+------------+------------+------+
| personid | recordid | item | filldate | dayssupply | gap |
+----------+----------+------+------------+------------+------+
| 1 | 1 | item | 2018-01-01 | 30 | NULL |
| 1 | 2 | item | 2018-02-01 | 30 | 1 |
| 1 | 3 | item | 2018-03-01 | 30 | 2 |
| 1 | 4 | item | 2018-05-01 | 30 | 31 |
| 1 | 5 | item | 2018-06-01 | 30 | 1 |
+----------+----------+------+------------+------------+------+
You can insert the results into a temp table and pull out only the ones you want (gap > 5), or use the query above as a CTE and pull out the results without the temp table.

Answer 2

This could be stated as follows: "Given a set of orders, return a subset for which there is no order within +/- 5 days of the expected resupply date (defined as txDate + DaysSupply)."
This can be solved simply with NOT EXISTS. Define the range of orders you wish to examine, and this query will find the subset of those orders for which there is no resupply order (NOT EXISTS) within 5 days of either side of the expected resupply date (txDate + daysSupply).
SELECT
gappedOrder.personID
, gappedOrder.recordID
, gappedOrder.item
, gappedOrder.txDate
, gappedOrder.daysSupply
FROM
recordTable as gappedOrder
WHERE
gappedOrder.item = 'desiredItem'
AND gappedOrder.txDate > '12/31/16'
AND gappedOrder.txDate < '1/1/18'
--order not refilled within date range tolerance
AND NOT EXISTS
(
SELECT
1
FROM
recordTable AS refilledOrder
WHERE
refilledOrder.personID = gappedOrder.personID
AND refilledOrder.item = gappedOrder.item
--5 days prior to (txDate + daysSupply)
AND refilledOrder.txtDate >= DATEADD(day, -5, DATEADD(day, gappedOrder.daysSupply, gappedOrder.txDate))
--5 days after (txtDate + daysSupply)
AND refilledOrder.txtDate <= DATEADD(day, 5, DATEADD(day, gappedOrder.daysSupply, gappedOrder.txtDate))
);