Query to run through each instance. MS-Access - sql

Question

I have a MS-Access database with two tables which I would like to query from, the basic table schema is shown below. I am looking to pull out the details for the earliest parish church in each parish – and in the instance that there is no church with ‘parish’ in the name; I would like to pull out the earliest church.
SITEDETAIL:
Site
Reference No. | Civil Parish | Site Name | NGR East | NGR North
1 Assynt Old Parish Church 6137 3172
2 Assynt St. Marys 6097 3870
3 Assynt New Parish Church 6249 3490
4 Bower Grimbister 2095 4067
5 Bower St. Andrews 2304 3194
6 Halkirk Firth Parish Church 7136 3450
7 Holm Strath Parish Church 4586 2045
8 Holm St Nicholas Parish 4132 3146
SITEDATES:
Site
Reference No. | Date
1 1812
2 1300
3 1900
4 1760
5 1750
6 1838
7 1619
8 1774
I have written a query that pulls out all the instances of ‘parish’:
SELECT SITEDETAIL.SITEREFNO, SITEDETAIL.CIVPARBUR_CDE, SITEDETAIL.SITENAME, SITEDETAIL.NGRE, SITEDETAIL.NGRN, SITEDATES.DATE
FROM SITEDETAIL INNER JOIN SITEDATES ON SITEDETAIL.SITEREFNO = SITEDATES.SITEREFNO
WHERE (((SITEDETAIL.SITENAME) Like "par*"));
However, this does not take into account the instances of multiple/no churches with ‘par*’ in the name.
Is it possible to create an SQL query that runs through each civil parish and selects the earliest ‘parish’ or earliest church, or is it necessary to write a perl script to run through them? Is this possible using DBI?
Desired output:
Site
Reference No. | Civil Parish | Site Name | NGR East | NGR North | Date
1 Assynt Old Parish Church 6137 3172 1812
5 Bower St. Andrews 2304 3194 1750
6 Halkirk Firth Parish Church 7136 3450 1838
7 Holm Strath Parish Church 4586 2045 1619
NB:In the case of Assynt, 'Old Parish Church' is selected despite being older because of having 'parish' in the name.

Answer 1

The following query should get you what you need. It's a little long, but it does the trick:
`select LIST.Civil_Parish, SD.Site_name, LIST.MSite_Date
from
(
select Civil_Parish, min(Site_date) as MSite_date
from SiteDetail
where Boolean = 1
group by Civil_Parish
union
select Civil_parish, min(Site_date) as MSite_date
from SiteDetail
where Civil_parish not in
(select Civil_parish
from SiteDetail
where Boolean = 1)
group by Civil_Parish) as LIST
left join sitedetail SD on LIST.Civil_Parish = SD.Civil_Parish and LIST.MSite_Date = SD.Site_Date`
Please note the following:
1) I am using PowerUser's boolean suggestion. If the Boolean column has value 1, then the row is a Parish Church, and 0 if it is not.
2) I combined the tables "SiteDates" and "SiteDetails" for the purpose of this example, as they are 1 to 1.
The core of the query is A) finding the oldest Parish church in a Parish, then B) find Parishes without Parish Churches.
The code for A) is as follows:
'select Civil_Parish, min(Site_date) as MSite_date
from SiteDetail
where Boolean = 1
group by Civil_Parish'
We then union that with the oldest churches in parishes that do not have a parish church:
'select Civil_parish, min(Site_date) as MSite_date
from SiteDetail
where Civil_parish not in
(select Civil_parish
from SiteDetail
where Boolean = 1)
group by Civil_Parish'
We then join the union query (named "LIST" here) with our original "SITEDETAIL" table on Parish and Date to bring in the church name.