SQL Statement Needed - results from a range but not within another range - sql

Question

I have two tables.
A MEMBERS table that lists all of the details about a member and
a second table that stores a historical record of all of the changes to each column
in the MEMBERS table. For example, if a member's status changed from Active to Frozen on June 1, the MEMBERCHANGES tables would have an entry stating that change.
I need to create a SQL Statement that lists all of the MEMBER records that are in a status of Freeze, who changed to the status in a date range but that there aren't any changes in a second date range.
For example, I need all member who changed to a status of FREEZE between Jan 1 and May 1 but who haven't had any changes to the status field from May 2 through Aug 31.
SELECT MEMBERS.scancode
,MEMBERS.fname
,MEMBERS.lname
,MEMBERTYPES.description
,MEMBERS.STATUS
,MEMBERS.email
,MEMBERS.datejoin
,MEMBERS.dateexpire
,MEMBERS.daterenewal
,MEMBERCHANGES.datechange
,MEMBERCHANGES.newvalue
FROM MEMBERS
INNER JOIN MEMBERCHANGES ON MEMBERS.memid = MEMBERCHANGES.memid
INNER JOIN MEMBERTYPES ON MEMBERS.mtypeid = MEMBERTYPES.mtypeid
AND NOT EXISTS (
SELECT MEMBERS.memid
FROM MEMBERS AS MEM2
INNER JOIN MEMBERCHANGES ON MEM2.memid = MEMBERCHANGES.memid
INNER JOIN MEMBERTYPES ON MEM2.mtypeid = MEMBERTYPES.mtypeid
WHERE (MEMBERCHANGES.columnname = 'status')
AND (MEMBERCHANGES.newvalue = 'F')
AND (
MEMBERCHANGES.datechange BETWEEN '2015-05-02'
AND '2015-08-31'
)
AND (MEM2.STATUS = 'F')
)
WHERE (MEMBERCHANGES.columnname = 'status')
AND (
MEMBERCHANGES.datechange BETWEEN '2015-01-01'
AND '2015-05-01'
)
AND (MEMBERS.STATUS = 'F')
AND (MEMBERCHANGES.newvalue = 'F')

Answer 1

I cleaned up your query with aliases and removed some things I think were redundant. Forgive me for changing to lowercase as well.
select ...
from
MEMBERS m
inner join MEMBERCHANGES on mc.memid = m.memid
inner join MEMBERTYPES on mt.mtypeid = m.mtypeid
where
/* current status is Freeze */
m.STATUS = 'F'
/* changed to Freeze between certain dates */
and mc.columnname = 'status'
and mc.datechange between '2015-01-01' and '2015-05-01'
and mc.newvalue = 'F'
/* and no changes between later dates */
and not exist (
select 1
from MEMBERCHANGES mc2
where
mc2.memid = mc.memid
and mc2.columnname = 'status'
and mc2.datechange between '2015-05-02' and '2015-08-31'
and mc2.newvalue = 'F'
)
Since current date is well past August 31 I'm wondering if you'll have a problem checking against the current status which could have changed in the last month and a half. I trust that you know the data you're dealing with.
It's also certainly possible that the status could have changed to Freeze during the first window but later changed to something else during the same window. And then its current status could be Freeze because of a change between September 1 and present date. I don't know if you need to check for that kind of thing but this query may not guarantee anything about the member status at the end of May 1st.