I have the following columns in a table called meetings: meeting_id - int, start_time - time, end_time - time. Assuming that this table has data for one calendar day only, how many minimum number of rooms do I need to accomodate all the meetings. Room size/number of people attending the meetings don't matter.
Here's the solution:
select * from
(select t.start_time,
t.end_time,
count(*) - 1 overlapping_meetings,
count(*) minimum_rooms_required,
group_concat(distinct concat(y.start_time,' to ',t.end_time)
separator ' // ') meeting_details from
(select 1 meeting_id, '08:00' start_time, '09:15' end_time union all
select 2, '13:20', '15:20' union all
select 3, '10:00', '14:00' union all
select 4, '13:55', '16:25' union all
select 5, '14:00', '17:45' union all
select 6, '14:05', '17:45') t left join
(select 1 meeting_id, '08:00' start_time, '09:15' end_time union all
select 2, '13:20', '15:20' union all
select 3, '10:00', '14:00' union all
select 4, '13:55', '16:25' union all
select 5, '14:00', '17:45' union all
select 6, '14:05', '17:45') y
on t.start_time between y.start_time and y.end_time
group by start_time, end_time) z;
My question - is there anything wrong with this answer? Even if there's nothing wrong with this, can someone share a better answer?
Let's say you have a table called 'meeting' like this -
Then You can use this query to get the minimum number of meeting Rooms required to accommodate all Meetings.
select max(minimum_rooms_required)
from (select count(*) minimum_rooms_required
from meetings t
left join meetings y on t.start_time >= y.start_time and t.start_time < y.end_time group by t.id
) z;
This looks clearer and simple and works fine.
Meetings can "overlap". So, GROUP BY start_time, end_time can't figure this out.
Not every algorithm can be done in SQL. Or, at least, it may be grossly inefficient.
I would use a real programming language for the computation, leaving the database for what it is good at -- being a data repository.
Build a array of 1440 (minutes in a day) entries; initialize to 0.
Foreach meeting:
Foreach minute in the meeting (excluding last minute):
increment element in array.
Find the largest element in the array -- the number of rooms needed.
CREATE TABLE [dbo].[Meetings](
[id] [int] NOT NULL,
[Starttime] [time](7) NOT NULL,
[EndTime] [time](7) NOT NULL) ON [PRIMARY] )GO
sample data set:
INSERT INTO Meetings VALUES (1,'8:00','09:00')
INSERT INTO Meetings VALUES (2,'8:00','10:00')
INSERT INTO Meetings VALUES (3,'10:00','11:00')
INSERT INTO Meetings VALUES (4,'11:00','12:00')
INSERT INTO Meetings VALUES (5,'11:00','13:00')
INSERT INTO Meetings VALUES (6,'13:00','14:00')
INSERT INTO Meetings VALUES (7,'13:00','15:00')
To Find Minimum number of rooms required run the below query:
create table #TempMeeting
(
id int,Starttime time,EndTime time,MeetingRoomNo int,Rownumber int
)
insert into #TempMeeting select id, Starttime,EndTime,0 as MeetingRoomNo,ROW_NUMBER()
over (order by starttime asc) as Rownumber from Meetings
declare #RowCounter int
select top 1 #RowCounter=Rownumber from #TempMeeting order by Rownumber
WHILE #RowCounter<=(Select count(*) from #TempMeeting)
BEGIN
update #TempMeeting set MeetingRoomNo=1
where Rownumber=(select top 1 Rownumber from #TempMeeting where
Rownumber>#RowCounter and Starttime>=(select top 1 EndTime from #TempMeeting
where Rownumber=#RowCounter)and MeetingRoomNo=0)set #RowCounter=#RowCounter+1
END
select count(*) from #TempMeeting where MeetingRoomNo=0
Consider a table meetings with columns id, start_time and end_time. Then the following query should give correct answer.
with mod_meetings as (select id, to_timestamp(start_time, 'HH24:MI')::TIME as start_time,
to_timestamp(end_time, 'HH24:MI')::TIME as end_time from meetings)
select CASE when max(a_cnt)>1 then max(a_cnt)+1
when max(a_cnt)=1 and max(b_cnt)=1 then 2 else 1 end as rooms
from
(select count(*) as a_cnt, a.id, count(b.id) as b_cnt from mod_meetings a left join mod_meetings b
on a.start_time>b.start_time and a.start_time<b.end_time group by a.id) join_table;
Sample DATA:
DROP TABLE IF EXISTS meeting;
CREATE TABLE "meeting" (
"meeting_id" INTEGER NOT NULL UNIQUE,
"start_time" TEXT NOT NULL,
"end_time" TEXT NOT NULL,
PRIMARY KEY("meeting_id")
);
INSERT INTO meeting values (1,'08:00','14:00');
INSERT INTO meeting values (2,'09:00','10:30');
INSERT INTO meeting values (3,'11:00','12:00');
INSERT INTO meeting values (4,'12:00','13:00');
INSERT INTO meeting values (5,'10:15','11:00');
INSERT INTO meeting values (6,'12:00','13:00');
INSERT INTO meeting values (7,'10:00','10:30');
INSERT INTO meeting values (8,'11:00','13:00');
INSERT INTO meeting values (9,'11:00','14:00');
INSERT INTO meeting values (10,'12:00','14:00');
INSERT INTO meeting values (11,'10:00','14:00');
INSERT INTO meeting values (12,'12:00','14:00');
INSERT INTO meeting values (13,'10:00','14:00');
INSERT INTO meeting values (14,'13:00','14:00');
Solution:
DROP VIEW IF EXISTS Final;
CREATE VIEW Final AS SELECT time, group_concat(event), sum(num) num from (
select start_time time, 's' event, 1 num from meeting
union all
select end_time time, 'e' event, -1 num from meeting)
group by 1
order by 1;
select max(room) AS Min_Rooms_Required FROM (
select
a.time,
sum(b.num) as room
from
Final a
, Final b
where a.time >= b.time
group by a.time
order by a.time
);
Here's the explanation to gashu's nicely working code (or otherwise a non-code explanation of how to solve it with any language).
Firstly, if the variable 'minimum_rooms_required' would be renamed to 'overlap' it would make the whole thing much easier to understand. Because for each of the start or end times we want to know the numbers of overlapping ongoing meetings. When we found the maximum, this means there's no way of getting around with less than the overlapping amount, because well they overlap.
By the way, I think there might be a mistake in the code. It should check for t.start_time or t.end_time between y.start_time and y.end_time. Counterexample: meeting 1 starts at 8:00, ends at 11:00 and meeting 2 starts at 10:00, ends at 12:00.
(I'd post it as a comment to the gashu's answerbut I don't have enough reputation)
I'd go for Lead() analytic function
select
sum(needs_room_ind) as min_rooms
from (
select
id,
start_time,
end_time,
case when lead(start_time,1) over (order by start_time asc) between start_time
and end_time then 1 else 0 end as needs_room_ind
from
meetings
) a
IMO, I wanna to take the difference between how many meeting are started and ended at the same time when each meeting_id is started (assuming meeting starts and ends on time)
my code was just like this :
with alpha as
(
select a.meeting_id,a.start_time,
count(distinct b.meeting_id) ttl_meeting_start_before,
count(distinct c.meeting_id) ttl_meeting_end_before
from meeting a
left join
(
select meeting_id,start_time from meeting
) b
on a.start_time > b.start_time
left join
(
select meeting_id,end_time from meeting
) c
on a.start_time > c.end_time
group by a.meeting_id,a.start_time
)
select max(ttl_meeting_start_before-ttl_meeting_end_before) max_meeting_room
from alpha
i have used the query function in SlamData.
My code:
SELECT
DATE_PART("year",thedate) AS year,DATE_PART("month",thedate) AS month,
SUM(runningPnL) AS PnL
FROM "/Mickey/testdb/sampledata3" AS c
GROUP BY DATE_PART("year", thedate) ,DATE_PART("month", thedate)
order by DATE_PART("year", thedate) ,DATE_PART("month", thedate)
The extract of my table:
PnL month year
-1651.8752 1 2001
17180.4776 2 2001
48207.54560000001 3 2001
Now, how can i find the cumulative sum of the PnL?
eg.-1651.8752 for the first month
15528.6024 for the second month
Thank you very much >.<
I am generating sample data same as you for cumulative sum. Hope from this you get some idea.
Create table tempData
(
pnl float,
[month] int,
[year] int
)
Go
insert into tempData values ( -1651.8752, 1,2001)
insert into tempData values ( 17180.4776, 2,2001)
insert into tempData values ( 48207.54560000001, 3,2001)
Select * , (SELECT SUM(Alias.pnl)
FROM tempData As Alias
WHERE Alias.[Month] <= tempData.[Month]
) As CumulativSUM
FROm tempData
ORDER BY tempData.[MOnth]
done
my code is
SELECT a1.year, a1.month, a1.PnL, a1.PnL/(SUM(a2.PnL)+125000) as Running_Total
FROM/Mickey/testdb/sampledata6as a1,/Mickey/testdb/sampledata6as a2
WHERE (a1.month > a2.month And a1.year=a2.year) or (a1.year>a2.year)
GROUP BY a1.year, a1.month,a1.PnL
ORDER BY a1.year,a1.month ASC;
Looking for MaxDate, its most recent date and the interval between. Of the MaxDate and most recent, I also need the quantities for each so I can also find the interval
Table "tblITEM_InventoryCount" structure is as follows:
Item_No Count Date Qty
001 08/29/2015 12
001 08/15/2015 17
001 07/15/2015 19
Item No 001
Max(CountDate) 08/29/2015
PriorCountDate 08/15/2015
Interval Days (MaxDate-RecentDate) 14
MaxDate Quantity 12
PriorCountDate Quantity 17
Interval Qty (17-12) 5
Currently using a query to find last two count dates for each ITEM_NO
SELECT tblITEM_InventoryCount.ITEM_NO, tblITEM_InventoryCount.Quantity, tblITEM_InventoryCount.CountDate
FROM tblITEM_InventoryCount
WHERE (((tblITEM_InventoryCount.CountDate)>=NthInGroup([tblITEM_InventoryCount].[ITEM_NO],2)))
ORDER BY tblITEM_InventoryCount.ITEM_NO, tblITEM_InventoryCount.CountDate DESC;
Then I am using a second query to calculate my data:
SELECT qryLAST2_InventoryCount_TRANSACTIONS.ITEM_NO, qryLAST2_InventoryCount_TRANSACTIONS.CountDate, (SELECT MAX([CountDate]) FROM [qryLAST2_InventoryCount_TRANSACTIONS] AS [Old Orders] WHERE [Old Orders].[CountDate] < [qryLAST2_InventoryCount_TRANSACTIONS].[CountDate] AND [Old Orders].[ITEM_NO] = [qryLAST2_InventoryCount_TRANSACTIONS].[ITEM_NO]) AS PriorCountDate, [CountDate]-[PriorCountDate] AS DaysInterval, qryLAST2_InventoryCount_TRANSACTIONS.Quantity, (SELECT Last([Quantity]) FROM [qryLAST2_InventoryCount_TRANSACTIONS] AS [OldCount] WHERE [OldCount].[Quantity] < [qryLAST2_InventoryCount_TRANSACTIONS].[Quantity] AND [OldCount].[ITEM_NO] = [qryLAST2_InventoryCount_TRANSACTIONS].[ITEM_NO]) AS PriorQuantity, [Quantity]-[PriorQuantity] AS QuantityInterval, [QuantityInterval]*30/[DaysInterval] AS [Usage]
FROM qryLAST2_InventoryCount_TRANSACTIONS
GROUP BY qryLAST2_InventoryCount_TRANSACTIONS.ITEM_NO, qryLAST2_InventoryCount_TRANSACTIONS.CountDate, qryLAST2_InventoryCount_TRANSACTIONS.Quantity
ORDER BY qryLAST2_InventoryCount_TRANSACTIONS.ITEM_NO, qryLAST2_InventoryCount_TRANSACTIONS.CountDate DESC;
I am not getting the results I need. The query returns two record lines for each item along with their max or last countdate, the previous countdate, intervaldays, qty, last qty, and interval.
I need max or last countdate and its qty count and prior countdate and its qty count.
Any help would be greatly appreciated.
Try this :
select
tab.item_no,
tab.Max_Date,
tab.PriorCountDate,
DateDiff ("d", tab.Max_Date, tab.PriorCountDate) as IntervalDays,
tab.MaxDateQty,
tab.PriorCountDateQty,
( tab.MaxDateQty-tab.PriorCountDateQty) as IntervalQty,
from
( select
temp1.item_no as item_no,
temp1.m as Max_Date,
(select MAX(count_date) from tblITEM_InventoryCount where count_date <> temp1.m ) as PriorCountDate,
temp1.q as MaxDateQty,
(select MAX(Qty) from tblITEM_InventoryCount where Qty <> temp1.q) as PriorCountDateQty,
from
( select item_no as i, Qty as q, MAX(count_date) as m
group by item_no, Qty ) as temp1
inner join
tblITEM_InventoryCount as temp2
on
temp1.item_no = temp2.item_no
)
as tab ;
SQL Fiddle
Table scheme:
CREATE TABLE company
(`company_id` int,`name` varchar(30))
;
INSERT INTO company
(`company_id`,`name`)
VALUES
(1,"Company A"),
(2,"Company B")
;
CREATE TABLE price
(`company_id` int,`price` int,`time` timestamp)
;
INSERT INTO price
(`company_id`,`price`,`time`)
VALUES
(1,50,'2015-02-21 02:34:40'),
(2,60,'2015-02-21 02:35:40'),
(1,70,'2015-02-21 05:34:40'),
(2,120,'2015-02-21 05:35:40'),
(1,150,'2015-02-22 02:34:40'),
(2,130,'2015-02-22 02:35:40'),
(1,170,'2015-02-22 05:34:40'),
(2,190,'2015-02-22 05:35:40')
I'm using Cron Jobs to fetch company prices. In concatenating the price history for each company, how can I make sure that only the last one in each day is included? In this case, I want all of the price records around 05:30am concatenated.
This is the result I'm trying to get (I have used Date(time) to only get the dates from the timestamps):
COMPANY_ID PRICE TIME
1 70|170 2015-02-21|2015-02-22
2 120|190 2015-02-21|2015-02-22
I have tried the following query but it doesn't work. The prices don't correspond to the dates and I don't know how to exclude all of the 2:30 am records before applying the Group_concat function.
SELECT company_id,price,trend_date FROM
(
SELECT company_id, GROUP_CONCAT(price SEPARATOR'|') AS price,
GROUP_CONCAT(trend_date SEPARATOR'|') AS trend_date
FROM
(
SELECT company_id,price,
DATE(time) AS trend_date
FROM price
ORDER BY time ASC
)x1
GROUP BY company_id
)t1
Can anyone show me how to get the desired result?
Ok, so this should work as intended:
SELECT p.company_id,
GROUP_CONCAT(price SEPARATOR '|') as price,
GROUP_CONCAT(PriceDate SEPARATOR '|') as trend_date
FROM price as p
INNER JOIN (SELECT company_id,
DATE(`time`) as PriceDate,
MAX(`time`) as MaxTime
FROM price
GROUP BY company_id,
DATE(`time`)) as t
ON p.company_id = t.company_id
AND p.`time` = t.MaxTime
GROUP BY p.company_id
Here is the modified sqlfiddle.
This is a bit unorthodox but I think it solves your problem:
SELECT company_id,
GROUP_CONCAT(price SEPARATOR'|'),
GROUP_CONCAT(trend_date SEPARATOR'|')
FROM (
SELECT *
FROM (
SELECT company_id,
DATE(`time`) `trend_date`,
price
FROM price
ORDER BY `time` DESC
) AS a
GROUP BY company_id, `trend_date`
) AS b
GROUP BY company_id
I have a table like this:
ID_____StartDate_____EndDate
----------------------------
1______05/01/2012___02/03/2013
2______06/30/2013___07/12/2013
3______02/17/2010___02/17/2013
4______12/10/2012___11/16/2013
I'm trying to get a count of the ID's that were active during each year. If the ID was active for multiple years, it would be counted multiple times. I don't want to "hardcode" years into my query because the data is over many many multiple years. (i.e. can't use CASE YEAR(StartDate) WHEN x then y or IF...
Desired Result from the table above:
YEAR_____COUNT
2010_____1
2011_____1
2012_____3
2013_____4
I've tried:
SELECT COUNT(ID)
FROM table
WHERE (DATE_FORMAT(StartDate, '%Y-%m') BETWEEN '2013-01' AND '2013-12'
OR DATE_FORMAT(EndDate, '%Y-%m') BETWEEN '2013-01' AND '2013-12')
of course this only is for the year 2013. I also tried:
SELECT YEAR(StartDate) AS 'Start Year', YEAR(EndDate) AS 'End Year', COUNT(id)
FROM table
WHERE StartDate IS NOT NULL
GROUP BY YEAR(StartDate);
though this gave me just those that started in a given year.
Assuming that there is an auxiliary table that contains consecutive numbers from 1 .. to X (where X must be grather than possible number of years in the table):
create table series( x int primary key auto_increment );
insert into series( x )
select null from information_schema.tables;
then the query might look like:
SELECT years.year, count(*)
FROM (
SELECT mm.min_year + s.x - 1 as year
FROM (
SELECT min( year( start_date )) min_year,
max( year( end_date )) max_year
FROM tab
) mm
JOIN series s
ON s.x <= mm.max_year - mm.min_year + 1
GROUP BY mm.min_year + s.x - 1
) years
JOIN tab
ON years.year between year( tab.start_date )
and year( tab.end_date )
GROUP BY years.year
;
see a demo: http://www.sqlfiddle.com/#!2/f49ab/14