Create an instance of a table in a single row? - sql

Question

I'm having trouble figuring out how to create a snapshot (or instance) of a table when the user updates the table in the UI.
The problem is:
I have a UI for "Amendments." In the UI, there is a dropdown list for "Amendment Type." Amendment Type also has its own UI, and the user can check/un-check the list of available Amendment Types here. When the user un-checks an Amendment Type, that type gets removed from the dropdown list for all Amendments. The client asks that changes to the Amendment Type ONLY affect NEW Amendments, and not ones that existed before the change.
So, if the Amendment Type values for "New, Draft, Closed" were checked previously, and "Draft" was un-checked, I would still need to display all three values in the UI for existing Amendments, and then only display "New" and "Closed" for new Amendments. But then, they can go back in and reopen the "Draft" and have that display once again, but only for Amendments created after they reopened it.
To me, this means that I need to create a table for "Amendment Type History." The table for "Amendment Type" has an AmendmentTypeID column where all of the IDs are displayed as rows. I would display those as columns, with the row defined by the Effective Date--the date that the values were changed. Then I would link the Amendment to the AmendmentTypeHistoryID and get the values to display by looking up the AmendmentTypeIDs.
e.g.
dbo.AmendmentType
AmendmentTypeID Name CreationDate IsActive
1 New 6/2/2019 1
2 Draft 6/2/2019 1
3 Closed 6/2/2019 1
dbo.AmendmentTypeHistory
AmendmentTypeHistoryID EffectiveDate AmendmentTypeID AmendmentTypeID AmendmentTypeID
1 6/3/2019 1 (New) 2 (Draft) 3 (Closed)
Then you change it...
dbo.AmendmentType
AmendmentTypeID Name CreationDate IsActive
1 New 6/2/2019 1
3 Closed 6/2/2019 1
dbo.AmendmentTypeHistory
AmendmentTypeHistoryID EffectiveDate AmendmentTypeID AmendmentTypeID AmendmentTypeID
1 6/3/2019 1 (New) 2 (Draft) 3 (Closed)
2 6/3/2019 1 (New) 3 (Closed) NULL
There are 77 Amendment Type possibilities total. It's not something I can hard code, so I was hoping I could do it dynamically somehow.
Does anyone know how I could do this? Is there an easier or better way to do what I'm trying to do?

Answer 1

This is a very difficult and confusing requirement. What happens if the Amendment Types which IsActive are different between the moment you load them into the drop down and the moment the user saves their entry?
Ignoring this, I would recommend a table which would map combinations in an ordered comma-seperated list. It is very rare that my answer breaks Normal Forms, but it would be difficult otherwise.
Make a table called AmendmentTypeGroup:
create table AmendmentTypeGroup
(
AmendmentTypeGroupID int identity
,AmendmentTypes nvarchar(max) not null
,constraint PK_AmendmentTypeGroup primary key clustered(AmendmentTypeGroupID)
)
Add a column to your Amendments (not amendments type) table:
alter table Amendmends add AmendmentTypeGroupID int null
Each time you insert a row in Amendments, use a trigger or proc to ensure you first insert into the AmendmentTypeGroup a group of all the IDs of all AmendmentTypes who are IsActive at that moment, get the group ID, and then insert the Amendments row with the group value you inserted. If there were already a group with the specific combination, just grab its id and use that instead.
declare #amendmentCombination nvarchar(max)
declare #groupID int
select amendmentCombination=string_agg(convert(nvarchar(max),AmendmentTypeID),',') WITHIN GROUP ( ORDER BY AmendmentTypeID asc)
from AmendmentType
where IsActive = 1 -- will only work for sql server version 2017. Search XML path concatenation if you don't have it
select #groupID=AmendmentTypeGroupID
from AmendmentTypeGroup
where AmendmentTypes=#amendmentCombination
if #groupID is null
begin
insert AmendmentTypeGroup(AmendmentTypes) select #amendmentCombination
set #groupID=SCOPE_IDENTITY() -- last id entered
end
insert Amendments(..your_other_columns...,AmendmentTypeGroup)
select ..your_other_columns...,#groupID
This way, for each Amendment row, you can join it with AmendmentTypeGroup to get the comma seperated list of available AmendmentTypes at that time. You will have to split it to take in in a tabular form.
To make your data more robust, you ought to 1) Manually create all AmendmentTypeGroups which were used for already existing rows in amendments, and insert their IDs in Amendment.AmendmentTypeGroup, so that you can then 2) create a FK on Amendment.AmendmentTypeGroup referenceing AmendmentTypeGroup.AmendmentTypeGroupID 3) create a unique constraint on AmendmentTypeGroup.AmendmentTypes
As you can see, this is difficult. Tread carefully.

Answer 2

After you comments I think I have a solution for you.
Create a table AmendmentTypeVersions like this
ID | VERSION_NUMBER | AmendmentTypeId
and insert all active AmendmentTypes using version 1
INSERT INTO AmendmentTypeVersions (VERSION_NUMBER , AmendmentTypeId)
SELECT 1, AmendmentTypeID
FROM AmendmentType
WHERE isactive = 1
Every time you have save the AmendmentType, get the max version number and insert the records of the new version
DECLARE #LastVersion = (SELECT MAX(VERSION_NUMBER) FROM AmendmentTypeVersions)
INSERT INTO AmendmentTypeVersions (VERSION_NUMBER , AmendmentTypeId)
SELECT #LastVersion + 1, AmendmentTypeID
FROM AmendmentType
WHERE isactive = 1
Add to column to Amendments with the VERSION_NUMBER and set it to 1
Now all you have to do is this:
When you are creating an Amendment you need to get then set the Amendment VERSION_NUMBER to the #lastVersion (On the edit operation you already have Amendment VERSION_NUMBER set)
always filter the AmendmentTypes by the VERSION_NUMBER of the Amendment (you have to join amendmentTypes with the AmendmentTypeVersions by the VERSION_NUMBER of the Amendment)