These are my tables:
Room (roomId, roomName, roomTypeId, roomStatus)
RoomType (roomTypeId, roomTypeName, roomTypeDesc, roomTypePrice)
ReservationRoom (reservationId, roomId,checkInDate, checkOutDate, totalStay)
I receive three parameter from user (check in date, check out date, quantity)to search the available room type that can be reserve into a grid view.
This is my sql that show the available roomtype for reserve.
SELECT rt.roomTypeName, rt.roomTypePrice, count(*) as quantity
FROM Room r,
RoomType rt
WHERE roomStatus = 'Online'
AND r.roomTypeId = rt.roomTypeId
AND NOT EXISTS (SELECT 1 FROM ReservationRoom b
WHERE b.roomId = r.roomId
AND (#CheckInDate BETWEEN b.checkInDate AND b.checkOutDate
OR #CheckOutDate BETWEEN b.checkInDate AND b.checkOutDate
OR (#CheckInDate<= b.checkInDate AND #CheckOutDate >= b.checkOutDate)))
group by rt.roomTypeName, rt.roomTypePrice
Having COUNT(*) >= #quantity";
It works quite well. But it got problem when my ReservationRoom table already have a record which is checkindate (1/11/2015) and check out date (2/11/2015) made by guest A for roomtypeA.
When a guest B search for room on check in date is(2/11/2015) and check out date is(3/11/2015).it will still show the roomtypeA is not available. But it should be available because the guest A already check out on 2/11. so is there any way to let user B reserve the roomtype in this situation?
You could convert from type DATE columns to DATETIME columns, and then compare specific times of day (i.e., your specific check-out time, such as 11am).
Or, convert all times to UNIX_TIMESTAMP, and then you will have simpler greater-than / less-than comparisons altogether, since it's just an integer.
use MySQL str_to_date or cast because you must need to convert your type as DATE
cast(str_to_date('1/11/2015','%d/%m/%Y')as date)
or
cast(str_to_date(checkindate,'%d/%m/%Y')as date)
Avoid using BETWEEN as it is inclusive of the two dates - see the reference material
Related
I have 2 tables, one with hostels (effectively a single-room hotel with lots of beds), and the other with bookings.
Hostel table: unique ID, total_spaces
Bookings table: start_date, end_date, num_guests, hostel_ID
I need a (My)SQL query to generate a list of all hostels that have at least num_guests free spaces between start_date and end_date.
Logical breakdown of what I'm trying to achieve:
For each hostel:
Get all bookings that overlap start_date and end_date
For each day between start_date and end_date, sum the total bookings for that day (taking into account num_guests for each booking) and compare with total_spaces, ensuring that there are at least num_guests spaces free on that day (if there aren't on any day then that hostel can be discounted from the results list)
Any suggestions on a query that would do this please? (I can modify the tables if necessary)
I built an example for you here, with more comments, which you can test out:
http://sqlfiddle.com/#!9/10219/9
What's probably tricky for you is to join ranges of overlapping dates. The way I would approach this problem is with a DATES table. It's kind of like a tally table, but for dates. If you join to the DATES table, you basically break down all the booking ranges into bookings for individual dates, and then you can filter and sum them all back up to the particular date range you care about. Helpful code for populating a DATES table can be found here: Get a list of dates between two dates and that's what I used in my example.
Other than that, the query basically follows the logical steps you've already outlined.
Ok, if you are using mysql 8.0.2 and above, then you can use window functions. In such case you can use the solution bellow. This solution does not need to compute the number of quests for each day in the query interval, but only focuses on days when there is some change in the number of hostel guests. Therefore, there is no helping table with dates.
with query as
(
select * from bookings where end_date > '2017-01-02' and start_date < '2017-01-05'
)
select hostel.*, bookingsSum.intervalMax
from hostel
join
(
select tmax.id, max(tmax.intervalCount) intervalMax
from
(
select hostel.id, t.dat, sum(coalesce(sum(t.gn),0)) over (partition by t.id order by t.dat) intervalCount
from hostel
left join
(
select id, start_date dat, guest_num as gn from query
union all
select id, end_date dat, -1 * guest_num as gn from query
) t on hostel.id = t.id
group by hostel.id, t.dat
) tmax
group by tmax.id
) bookingsSum on hostel.id = bookingsSum.id and hostel.total_spaces >= bookingsSum.intervalMax + <num_of_people_you_want_accomodate>
demo
It uses a simple trick, where each start_date represents +guest_num to the overall number of quests and each 'end_date' represents -guest_num to the overall number of quests. We than do the necessary sumarizations in order to find peak number of quests (intervalMax) in the query interval.
You change '2017-01-05' in my query to '2017-01-06' (then only two hostels are in the result) and if you use '2017-01-07' then just hostel id 3 is in the result, since it does not have any bookings yet.
SELECT * FROM table WHERE '2016-03-31' > (SELECT MAX(year) from table where bill_id = 'somevalue')
I am using above query to check if 2016-03-31 is greater than all years present in table against bill_id. It is working fine. but is it correct approach to compare dates. dates will always in above format. Is there any need to convert date format for comparison. value 2016-03-31 will change dynamically but it will be always in Y-m-d format
Note : year is column name which contains full date in Y-m-d format like 2016-05-20
You are not comparing dates. You are comparing a string '2016-03-31' with a number, e.g. 2015.
In order to compare, MySQL silently converts the string to number. One would expect this to crash, as '2016-03-31' certainly isn't a number. MySQL, however, reads from left to right and takes from there all that can be considered a number, i.e. '2016'. Well, one could argue that some people put a minus sign at the end of a number, so this should be '2016-', i.e. -2016. Anyway, MySQL stops before the minus sign, gets 2016 and uses this for the comparision.
I don't know if all this is guaranteed to work in the future. I would not rely on this.
What result would you expect anyway? Is the 31st of March 2016 greater than the year 2016? That's a queer question, don't you think?
Try this. But do you really have a column year that stores only year?
SELECT * FROM table WHERE year(STR_TO_DATE('2016-03-31'))
> (SELECT MAX(year) from table where bill_id = 'somevalue')
SELECT * FROM table WHERE YEAR('2016-03-31') > (SELECT MAX(year) from table where bill_id = 'somevalue')
MySQL YEAR() returns the year for a given date or timestamp. The return value is in the range of 1000 to 9999 or 0 for 'zero' date.
For the purposes of my question, I have a database in a MySQL server with info on many taxi rides (it is comprised of two tables, history_trips and trip_info).
In history_trips, each row's useful data is comprised of a unique alphanumeric ID, ride_id, the name of the rider, rider, and the time the ride ended, finishTime as a Y-m-d string.
In trip_info, each row's useful data similarly contains ride_id and rider, but also contains an integer, value (calculated in the back end from other data).
What I need to do is create a query that can find the average of all the maximum 'values' from all riders in a given time period. The riders included in this average are only considered if they completed less than X (let's say 3) rides within the aforementioned time period.
So far, I have a query that creates a grouped table containing the name of the rider, the finishTime of their highest 'value' ride, the value of said ride, and the number of rides, num_rides, they have taken in that time period. The AVG(b.value) column, however, gives me the same values as b.value, which is unexpected. I would like to find some way to return the average of the b.value column.
SELECT a.rider, a.finishTime, b.value, AVG(b.value), COUNT(a.rider) as num_rides
FROM history_trips as a, trip_info as b
WHERE a.finishTime > 'arbitrary_start_date_str' and a.ride_id = b.ride_id
and b.value = (SELECT MAX(value)
from trip_info where rider = b.rider and ride_id = b.ride_id)
GROUP BY a.rider
HAVING COUNT(a.rider) < 3
I am a novice in SQL but have read on some other forums that when using the AVG function on a value you must also GROUP BY that value. I was wondering if there is a way around that or if I am thinking of this problem incorrectly. Thanks in advance for any advice / solutions you might have!
The following worked for me:
SELECT AVG(ridergroups.maxvalues) avgmaxvalues FROM
(SELECT MAX(trip_info.value) maxvalues FROM trip_info
INNER JOIN history_trips
ON trip_info.rideid = history_trips.ride_id
WHERE history_trips.finishTime > '2010-06-20'
GROUP BY trip_info.rider
HAVING COUNT(trip_info.rider) < 3) ridergroups;
The subquery groups the maximum values by rider after filtering by date and rider count. The containing query calculates the average of the maximum values.
The question I am working on is as follows:
What is the difference in the amount received for each month of 2004 compared to 2003?
This is what I have so far,
SELECT #2003 = (SELECT sum(amount) FROM Payments, Orders
WHERE YEAR(orderDate) = 2003
AND Payments.customerNumber = Orders.customerNumber
GROUP BY MONTH(orderDate));
SELECT #2004 = (SELECT sum(amount) FROM Payments, Orders
WHERE YEAR(orderDate) = 2004
AND Payments.customerNumber = Orders.customerNumber
GROUP BY MONTH(orderDate));
SELECT MONTH(orderDate), (#2004 - #2003) AS Diff
FROM Payments, Orders
WHERE Orders.customerNumber = Payments.customerNumber
Group By MONTH(orderDate);
In the output I am getting the months but for Diff I am getting NULL please help. Thanks
I cannot test this because I don't have your tables, but try something like this:
SELECT a.orderMonth, (a.orderTotal - b.orderTotal ) AS Diff
FROM
(SELECT MONTH(orderDate) as orderMonth,sum(amount) as orderTotal
FROM Payments, Orders
WHERE YEAR(orderDate) = 2004
AND Payments.customerNumber = Orders.customerNumber
GROUP BY MONTH(orderDate)) as a,
(SELECT MONTH(orderDate) as orderMonth,sum(amount) as orderTotal FROM Payments, Orders
WHERE YEAR(orderDate) = 2003
AND Payments.customerNumber = Orders.customerNumber
GROUP BY MONTH(orderDate)) as b
WHERE a.orderMonth=b.orderMonth
Q: How do I subtract two declared variables in MySQL.
A: You'd first have to DECLARE them. In the context of a MySQL stored program. But those variable names wouldn't begin with an at sign character. Variable names that start with an at sign # character are user-defined variables. And there is no DECLARE statement for them, we can't declare them to be a particular type.
To subtract them within a SQL statement
SELECT #foo - #bar AS diff
Note that MySQL user-defined variables are scalar values.
Assignment of a value to a user-defined variable in a SELECT statement is done with the Pascal style assignment operator :=. In an expression in a SELECT statement, the equals sign is an equality comparison operator.
As a simple example of how to assign a value in a SQL SELECT statement
SELECT #foo := '123.45' ;
In the OP queries, there's no assignment being done. The equals sign is a comparison, of the scalar value to the return from a subquery. Are those first statements actually running without throwing an error?
User-defined variables are probably not necessary to solve this problem.
You want to return how many rows? Sounds like you want one for each month. We'll assume that by "year" we're referring to a calendar year, as in January through December. (We might want to check that assumption. Just so we don't find out way too late, that what was meant was the "fiscal year", running from July through June, or something.)
How can we get a list of months? Looks like you've got a start. We can use a GROUP BY or a DISTINCT.
The question was... "What is the difference in the amount received ... "
So, we want amount received. Would that be the amount of payments we received? Or the amount of orders that we received? (Are we taking orders and receiving payments? Or are we placing orders and making payments?)
When I think of "amount received", I'm thinking in terms of income.
Given the only two tables that we see, I'm thinking we're filling orders and receiving payments. (I probably want to check that, so when I'm done, I'm not told... "oh, we meant the number of orders we received" and/or "the payments table is the payments we made, the 'amount we received' is in some other table"
We're going to assume that there's a column that identifies the "date" that a payment was received, and that the datatype of that column is DATE (or DATETIME or TIMESTAMP), some type that we can reliably determine what "month" a payment was received in.
To get a list of months that we received payments in, in 2003...
SELECT MONTH(p.payment_received_date)
FROM payment_received p
WHERE p.payment_received_date >= '2003-01-01'
AND p.payment_received_date < '2004-01-01'
GROUP BY MONTH(p.payment_received_date)
ORDER BY MONTH(p.payment_received_date)
That should get us twelve rows. Unless we didn't receive any payments in a given month. Then we might only get 11 rows. Or 10. Or, if we didn't receive any payments in all of 2003, we won't get any rows back.
For performance, we want to have our predicates (conditions in the WHERE clause0 reference bare columns. With an appropriate index available, MySQL will make effective use of an index range scan operation. If we wrap the columns in a function, e.g.
WHERE YEAR(p.payment_received_date) = 2003
With that, we will be forcing MySQL to evaluate that function on every flipping row in the table, and then compare the return from the function to the literal. We prefer not do do that, and reference bare columns in predicates (conditions in the WHERE clause).
We could repeat the same query to get the payments received in 2004. All we need to do is change the date literals.
Or, we could get all the rows in 2003 and 2004 all together, and collapse that into a list of distinct months.
We can use conditional aggregation. Since we're using calendar years, I'll use the YEAR() shortcut (rather than a range check). Here, we're not as concerned with using a bare column inside the expression.
SELECT MONTH(p.payment_received_date) AS `mm`
, MAX(MONTHNAME(p.payment_received_date)) AS `month`
, SUM(IF(YEAR(p.payment_received_date)=2004,p.payment_amount,0)) AS `2004_month_total`
, SUM(IF(YEAR(p.payment_received_date)=2003,p.payment_amount,0)) AS `2003_month_total`
, SUM(IF(YEAR(p.payment_received_date)=2004,p.payment_amount,0))
- SUM(IF(YEAR(p.payment_received_date)=2003,p.payment_amount,0)) AS `2004_2003_diff`
FROM payment_received p
WHERE p.payment_received_date >= '2003-01-01'
AND p.payment_received_date < '2005-01-01'
GROUP
BY MONTH(p.payment_received_date)
ORDER
BY MONTH(p.payment_received_date)
If this is a homework problem, I strongly recommend you work on this problem yourself. There are other query patterns that will return an equivalent result.
I think this is the problem:
In #2003 and #2004, you select only the sum. And even if you group by the month you still select one column i.e. each row does not say what month it is select for. So when you try to subtract SQL asks which row in #2003 should be subtracted from #2004.
So I think the solution is to select the month with the sum and do the subtract later based on the month.
I have 2 tables: Product, User.
Product:
Date(Datetime)
Phone_Number(Number).
User:
Date (Datetime)
Phone_Number(Number)
Type(Value of N or C).
When a new user is added to the User table, it is given a date, Phone Number and value of "N" (N for New).
When a user gets cancelled, it is given a date, the Phone Number and value of "C" (C for Cancelled).
Using MySQL, I need to find out the date difference between the Date the user was created and the date the user was cancelled and if they had a product (can match the user to the product by Phone Number) between the date of the creation and the date of the cancellation.
Any assistance would be greatly appreciated as my Query writing isn't terrible but this I can't work out.
Thanks.
You need to start by self-joining the User table to find the created and cancelled dates. Then join to the Product table to see if anything is there.
SELECT u.Phone_Number, u.Created, u.Cancelled, p.Date as 'ProductDate'
FROM (
SELECT u1.Phone_Number, u1.Date as 'Created', u2.Date as 'Cancelled'
FROM User u1
JOIN User u2 on u1.Phone_Number=u2.Phone_Number
WHERE u1.Type = 'N'
and u2.Type = 'C'
) u
LEFT JOIN Product p on u.Phone_Number = p.Phone_Number
and p.Date between u.Created and u.Cancelled
SELECT
/* Anything you want from the User table */
/* CASE statement that checks if prod.phone_number is not null which means a product was present */
FROM
User user_new
JOIN User user_can
ON user_new.phone_number = user_can.phone_number
LEFT JOIN Product prod
ON prod.phone_number = user_new.phone_number
WHERE
(prod.Date IS NULL) OR -- Either there was no record.
(prod.Date BETWEEN user_new.Date AND user_can.Date) -- or a product existed between the two dates.
It doesn't sound like your table will have the required data to determine the difference between the date the user is created and cancelled if you're only storing one date field. But if you had 2 columns, user.createdDate and user.cancelledDate you could use
SELECT DATEDIFF(user.createdDate, user.cancelledDated) AS DiffDate
I don't know if DATEDIFF works with datetime objects, I've used it with plain dates formatted like "year-mm-dd" and it will give you a Query result object with DiffDate, an integer of the number of days.
If user.cancelledDate is before user.createdDate, you will get a negative integer.