Hi I am doing a project where I am stuck in the following the question asks me to make a booking entry for a travel agency using previous records such as bookingid, customerid, flightID number, passenger details etc and also the booking can have a status of reserved or held . If the seat is confirmed right away it is reserved and if not the passenger has 24 hrs to reserve and change it from held to reserve status. Also, if the seat isn't booked after 24 hrs it changes to expired status.
so far what I was able to come up with is
INSERT (values) INTO the different tables and when it is booked right bookingid.status = R or bookingid.status = bookingtime > 24 = E
without a clue here so appreciate some help !!!
There are many ways of doing this, but the easiest would be to initialize the booking status to reserved if it is booked right away and if it's not you would put held. Now, you would have to rely on a view (or another similar approach) to get the dynamically calculated status. If the user reserves his booking at a later time, you simply have to update the booking status to reserve.
Note that I dont necessary suggest to represent statuses as strings, its just for the example.
SELECT
CASE
WHEN status = 'held' AND DATEDIFF(hh, booking_date, now()) > 24 THEN 'expired'
ELSE status
END AS status
FROM booking
Related
I have a table which contains the products details, If it is a new product the status will be 1.
Once it got purchased, the status will change to 2.
My requirement is to send mail to the owner if the product remains in status 1 for more than 5 minutes.
Help me out to proceed further, what are all the ways to do so.
Maybe you can add a field like "LastStatusChangedOn", which is a DateTime (or a DateTimeOffset if you need to keep account with different time zones).
And then just select all Products where the difference between the current time and the LastStatusChangedOn is greater than 5 minutes.
Without the exact database structure, it's impossible to give a complete sample, but something like this?
SELECT * FROM Products WHERE DateDiff(minute, LastStatusChangeOn, getdate()) > 5
The table below contains customer reservations. Customers come and make one record in this table, and the last day this table will be updated its checkout_date field by putting that current time.
The Table
Now I need to extract all customers spending nights.
The Query
SELECT reservations.customerid, reservations.roomno, rooms.rate,
reservations.checkin_date, reservations.billed_nights, reservations.status,
DateDiff("d",reservations.checkin_date,Date())+Abs(DateDiff("s",#12/30/1899
14:30:0#,Time())>0) AS Due_nights FROM reservations, rooms WHERE
reservations.roomno=rooms.roomno;
What I need is, if customer has checkout status, due nights will be calculated checkin_date subtracting by checkout date instead current date, also if customer has checkout date no need to add extra absolute value from 14:30.
My current query view is below, also my computer time is 14:39 so it adds 1 to every query.
Since you want to calculate the Due nights upto the checkout date, and if they are still checked in use current date. I would suggest you to use an Immediate If.
The condition to check would be the status of the room. If it is checkout, then use the checkout_date, else use the Now(), something like.
SELECT
reservations.customerid,
reservations.roomno,
rooms.rate,
reservations.checkin_date,
reservations.billed_nights,
reservations.status,
DateDiff("d", checkin_date, IIF(status = 'checkout', checkout_date, Now())) As DueNights
FROM
reservations
INNER JOIN
rooms
ON reservations.roomno = rooms.roomno;
As you might have noticed, I used a JOIN. This is more efficient than merging the two tables with common identifier. Hope this helps !
This is really frustrating me.
So, I'm making a database recording people joining and leaving our office, as well as changing roles, in order to keep track of headcount. This is succinctly recorded in the following table:
EmployeeID | RoleID | FTE | Date
FTE is the proportion of full-time hours the role is worth (i.e. 1 is full-time, 0.5 is part-time, etc). Leaving events are recorded as changing the role to 0 (Absent) and FTE to 0. The trouble is, people can have more than one role, which means that the number of hours they actually worked is a composite of all the events for that employee that occur on the same day. So if someone goes from full time on one project to splitting their time between two projects, a ChangeRole event is logged for each.
So I want to know the total headcount on a monthly basis. Essentially the query I would want is "Select all records from this table where, for each EmployeeID, the date is the maximum date below a specified date." From there I can sum the FTE to get the headcount.
Now I can get some of those things in isolation: I can do max(date), I can do criteria:<#dd/mm/yyyy##. But for some reason I can't seem to combine it all to get what I want, and I'm at a point where I've been staring at the problem so long that it doesn't make sense to me. Can anyone help me out? Thanks!
Something like this?
SELECT Events.*
FROM Events INNER JOIN (
SELECT EmployeeID, Max(Date) AS LatestDate
FROM Events
WHERE Events.Date < [Date entered]
GROUP BY EmployeeID) AS S
ON (Events.EmployeeID = S.EmployeeID) AND (Events.Date = S.LatestDate)
I am working on an Hotel DB, and the booking table changes a lot since people book and cancel reservation all the time. Trying to find out the best way to convert the booking table to a fact table in SSAS. I want to be able to get the right statsics from it.
For example: if a client X booked a room on Sep 20th for Dec 20th and canceled the order on Oct 20th. If I run the cube on the month of September (run it in Nov) and I want to see how many rooms got booked in the month of Sep, the order X made should be counted in the sum.
However, if I run the cube for YTD calculation (run it in Nov), the order shouldn't be counted in the sum.
I was thinking about inserting the updates to the same fact table every night, and in addition to the booking number (unique key) and add revision column to the table. So going back to the example, let say client X booking number is 1234, the first time I enter it to the table will get revision 0, in Oct when I add the cancellation record, it will get revision 1 (of course with timestamp on the row).
Now, if I want to look on any piroed of time, I can take it by the timestamp and look at the MAX(revision).
Does it make sense? Any ideas?
NOTE: I gave the example of cancelling the order, but we want to track another statistics.
Another option I read about is partitioning the cubes, but do I partition the entire table. I want to be able to add changes every night. Will I need to partition the entire table every night? it's a huge table.
One way to handle this is to insert records in your fact table for bookings and cancellations. You don't need to look at the max(revision) - cubes are all about aggregation.
If your table looks like this:
booking number, date, rooms booked
You can enter data like this:
00001, 9/10, 1
00002, 9/12, 1
00001, 10/5, -1
Then your YTDs will always have information accurate as of whatever month you're looking at. Simply sum up the booked rooms.
I want to record user states and then be able to report historically based on the record of changes we've kept. I'm trying to do this in SQL (using PostgreSQL) and I have a proposed structure for recording user changes like the following.
CREATE TABLE users (
userid SERIAL NOT NULL PRIMARY KEY,
name VARCHAR(40),
status CHAR NOT NULL
);
CREATE TABLE status_log (
logid SERIAL,
userid INTEGER NOT NULL REFERENCES users(userid),
status CHAR NOT NULL,
logcreated TIMESTAMP
);
That's my proposed table structure, based on the data.
For the status field 'a' represents an active user and 's' represents a suspended user,
INSERT INTO status_log (userid, status, logcreated) VALUES (1, 's', '2008-01-01');
INSERT INTO status_log (userid, status, logcreated) VALUES (1, 'a', '2008-02-01');
So this user was suspended on 1st Jan and active again on 1st of February.
If I wanted to get a suspended list of customers on 15th January 2008, then userid 1 should show up. If I get a suspended list of customers on 15th February 2008, then userid 1 should not show up.
1) Is this the best way to structure this data for this kind of query?
2) How do I query the data in either this structure or in your proposed modified structure so that I can simply have a date (say 15th January) and find a list of customers that had an active status on that date in SQL only? Is this a job for SQL?
This can be done, but would be a lot more efficient if you stored the end date of each log. With your model you have to do something like:
select l1.userid
from status_log l1
where l1.status='s'
and l1.logcreated = (select max(l2.logcreated)
from status_log l2
where l2.userid = l1.userid
and l2.logcreated <= date '2008-02-15'
);
With the additional column it woud be more like:
select userid
from status_log
where status='s'
and logcreated <= date '2008-02-15'
and logsuperseded >= date '2008-02-15';
(Apologies for any syntax errors, I don't know Postgresql.)
To address some further issues raised by Phil:
A user might get moved from active, to suspended, to cancelled, to active again. This is a simplified version, in reality, there are even more states and people can be moved directly from one state to another.
This would appear in the table like this:
userid from to status
FRED 2008-01-01 2008-01-31 s
FRED 2008-02-01 2008-02-07 c
FRED 2008-02-08 a
I used a null for the "to" date of the current record. I could have used a future date like 2999-12-31 but null is preferable in some ways.
Additionally, there would be no "end date" for the current status either, so I think this slightly breaks your query?
Yes, my query would have to be re-written as
select userid
from status_log
where status='s'
and logcreated <= date '2008-02-15'
and (logsuperseded is null or logsuperseded >= date '2008-02-15');
A downside of this design is that whenever the user's status changes you have to end date their current status_log as well as create a new one. However, that isn't difficult, and I think the query advantage probably outweighs this.
Does Postgres support analytic queries? This would give the active users on 2008-02-15
select userid
from
(
select logid,
userid,
status,
logcreated,
max(logcreated) over (partition by userid) max_logcreated_by_user
from status_log
where logcreated <= date '2008-02-15'
)
where logcreated = max_logcreated_by_user
and status = 'a'
/
#Tony the "end" date isn't necessarily applicable.
A user might get moved from active, to suspended, to cancelled, to active again. This is a simplified version, in reality, there are even more states and people can be moved directly from one state to another.
Additionally, there would be no "end date" for the current status either, so I think this slightly breaks your query?
#Phil
I like Tony's solution. It seems to most approriately model the situation described. Any particular user has a status for a given period of time (a minute, an hour, a day, etc.), but it is for a duration, not an instant in time. Since you want to know who was active during a certain period of time, modeling the information as a duration seems like the best approach.
I am not sure that additional statuses are a problem. If someone is active, then suspended, then cancelled, then active again, each of those statuses would be applicable for a given duration, would they not? It may be a vey short duration, such as a few seconds or a minute, but they would still be for a length of time.
Are you concerned that a person's status can change multiple times in a given day, but you want to know who was active for a given day? If so, then you just need to more specifically define what it means to be active on a given day. If it is enough that they were active for any part of that day, then Tony's answer works well as is. If they would have to be active for a certain amount of time in a given day, then Tony's solution could be modified to simply determine the length of time (in hours, or minutes, or days), and adding further restrictions in the WHERE clause to retrieve for the proper date, status, and length of time in that status.
As for there being no "end date" for the current status, that is no problem either as long as the end date were nullable. Simply use something like this "WHERE enddate <= '2008-08-15' or enddate is null".