I am trying to create a calculated field in an Access DB however am having trouble working out how to best do it.
The field is “Duration” which needs to be the difference between two “SecsLapsed” values. These values all are assigned an “order” which is the sequence of the data/observed events ie 1, 2, 3, 4, etc..
Order one will always be Secslapsed = 0 (as it is the beginning of the record)
Following records need to calculate duration from the difference between secslapsed values for example for Order2, duration = Secslapsed(for orde3) – Secslapsed (for order2). The order value in the equation however must be relative to the order record ie. Order10 will calculate difference between secslapsed for order11 – secslapsed for order10.
Any ideas? 😊
Given a table Table1 with your mentioned numeric field Duration this would be your query:
Select
Duration,
Duration - Nz(
(Select Top 1 Duration From Table1 As Sub Where Sub.Duration < Table1.Duration Order By duration Desc)
,0) As SecsLapsed
From Table1
If there also is a field like Project in your table to separate such 'duration packages', you could use this:
Select
Project, Duration,
Duration - Nz(
(Select Top 1 Duration From Table1 As Sub Where Sub.Project = Table1.Project And Sub.Duration < Table1.Duration Order By duration Desc)
,0) As SecsLapsed
From Table1
Order By Project, Duration
Related
I have a table containing stock market data (open, hi, lo, close prices) but in a random order of date:
Date Open Hi Lo Close
12/10/2019 313.82 314.54 312.81 313.58
11/22/2019 311.09 311.24 309.85 310.96
11/25/2019 311.98 313.37 311.98 313.37
11/26/2019 313.41 314.28 313.06 314.08
11/27/2019 314.61 315.48 314.37 315.48
11/29/2019 314.86 315.13 314.06 314.31
12/2/2019 314.59 314.66 311.17 311.64
12/3/2019 308.65 309.64 307.13 309.55
I have another value in a PHP variable (say $BaseValue),and a start date and end date ($startdt and $enddt).
1) My requirement is to pick-up the value from the HI column, if it exceeds the $BaseValue on the very FIRST date in a chronological order between the given start and end dates.
For example, if the $BaseValue=314, startdt=11/22, enddt=12/2, then I want to retrieve the Date (11/26/19) as it is the earliest date on which the Hi value (314.28) exceeded the $Basevalue within the given date range. The select statement should return both the Hi value (314.28) and the Date (11/26/19).
2) Additionally, I also need to retrieve the HIGHEST value and date from the HI column during the given date duration. In the above scenario, it should return 315.48 and corresponding date 11/27.
The table is NOT in a chronological order - its randomly filled.
I am unable to get the first query at all with the use of MAX function and its various combinations. Makes me wonder if that is possible at all in SQL or not.
While the second is straightforward, I was wondering if it is more efficient and less complex to club the two queries and get the four values in one single shot.
Any ideas on how can I approach the need to fulfill this requirement please?
Thanks
You could use two subqueries for filtering, one per criteria, like:
select t.*
from mytable t
where
t.date = (
select min(t1.date)
from mytable t1
where t1.date between :datedt and :enddt and t1.hi >= :basevalue
)
or t.hi = (
select max(t1.hi)
from mytable t1
where t1.date between datedt and :enddt and t1.hi >= :basevalue
)
Another option is to union two queries with orer by and limit:
(
select t.*
from mytable
where t.date between :datedt and :enddt and t1.hi >= :basevalue
order by t.date
limit 1
)
union
(
select t.*
from mytable t
where t.date between :datedt and :enddt and t1.hi >= :basevalue
order by t.hi desc, t.date
limit 1
)
Please note that both queries do not do exactly the same thing. If there are ties for the highest hi in the period, the first query will return all ties, while the second will pick the earliest one. It's up to you to decide which solution better fits your use case.
I have a MySQL table shown in a picture. The result I want to get is in the "average" column:
I would like create query to calculate the average value since the beginning of the year (1 January). Each row contains the average between the beginning of the year and current row. Each 1 January the average should be reset to zero.
One method uses a correlated subquery:
select date, value,
(select avg(value) from t t2 where t2.date <= t.date) as running_avg
from t
order by date;
This makes some assumptions:
"a", "b" and so on are numbers, not strings.
a+b/2 really means (a + b) / 2 and so on.
If you need from only this year, then the condition needs to include the year.
I currently have an employee logging sql table that has 3 columns
fromState: String,
toState: String,
timestamp: DateTime
fromState is either In or Out. In means employee came in and Out means employee went out. Each row can only transition from In to Out or Out to In.
I'd like to generate a temporary table in sql to keep track during a given hour (hour by hour), how many employees are there in the company. Aka, resulting table has columns HourBucket, NumEmployees.
In non-SQL code I can do this by initializing the numEmployees as 0 and go through the table row by row (sorted by timestamp) and add (employee came in) or subtract (went out) to numEmployees (bucketed by timestamp hour).
I'm clueless as how to do this in SQL. Any clues?
Use a COUNT ... GROUP BY query. Can't see what you're using toState from your description though! Also, assuming you have an employeeID field.
E.g.
SELECT fromState AS 'Status', COUNT(*) AS 'Number'
FROM StaffinBuildingTable
INNER JOIN (SELECT employeeID AS 'empID', MAX(timestamp) AS 'latest' FROM StaffinBuildingTable GROUP BY employeeID) AS LastEntry ON StaffinBuildingTable.employeeID = LastEntry.empID
GROUP BY fromState
The LastEntry subquery will produce a list of employeeIDs limited to the last timestamp for each employee.
The INNER JOIN will limit the main table to just the employeeIDs that match both sides.
The outer GROUP BY produces the count.
SELECT HOUR(SBT.timestamp) AS 'Hour', SBT.fromState AS 'Status', COUNT(*) AS 'Number'
FROM StaffinBuildingTable AS SBT
INNER JOIN (
SELECT SBIJ.employeeID AS 'empID', MAX(timestamp) AS 'latest'
FROM StaffinBuildingTable AS SBIJ
WHERE DATE(SBIJ.timestamp) = CURDATE()
GROUP BY SBIJ.employeeID) AS LastEntry ON SBT.employeeID = LastEntry.empID
GROUP BY SBT.fromState, HOUR(SBT.timestamp)
Replace CURDATE() with whatever date you are interested in.
Note this is non-optimal as it calculates the HOUR twice - once for the data and once for the group.
Again you are using the INNER JOIN to limit the number of returned row, this time to the last timestamp on a given day.
To me your description of the FromState and ToState seem the wrong way round, I'd expect to doing this based on the ToState. But assuming I'm wrong on that the following should point you in the right direction:
First, I create a "Numbers" table containing 24 rows one for each hour of the day:
create table tblHours
(Number int);
insert into tblHours values
(0),(1),(2),(3),(4),(5),(6),(7),
(8),(9),(10),(11),(12),(13),(14),(15),
(16),(17),(18),(19),(20),(21),(22),(23);
Then for each date in your employee logging table, I create a row in another new table to contain your counts:
create table tblDailyHours
(
HourBucket datetime,
NumEmployees int
);
insert into tblDailyHours (HourBucket, NumEmployees)
select distinct
date_add(date(t.timeStamp), interval h.Number HOUR) as HourBucket,
0 as NumEmployees
from
tblEmployeeLogging t
CROSS JOIN tblHours h;
Then I update this table to contain all the relevant counts:
update tblDailyHours h
join
(select
h2.HourBucket,
sum(case when el.fromState = 'In' then 1 else -1 end) as cnt
from
tblDailyHours h2
join tblEmployeeLogging el on
h2.HourBucket >= el.timeStamp
group by h2.HourBucket
) cnt ON
h.HourBucket = cnt.HourBucket
set NumEmployees = cnt.cnt;
You can now retrieve the counts with
select *
from tblDailyHours
order by HourBucket;
The counts give the number on site at each of the times displayed, if you want during the hour in question, we'd need to tweak this a little.
There is a working version of this code (using not very realistic data in the logging table) here: rextester.com/DYOR23344
Original Answer (Based on a single over all count)
If you're happy to search over all rows, and want the current "head count" you can use this:
select
sum(case when t.FromState = 'In' then 1 else -1) as Heads
from
MyTable t
But if you know that there will always be no-one there at midnight, you can add a where clause to prevent it looking at more rows than it needs to:
where
date(t.timestamp) = curdate()
Again, on the assumption that the head count reaches zero at midnight, you can generalise that method to get a headcount at any time as follows:
where
date(t.timestamp) = "CENSUS DATE" AND
t.timestamp <= "CENSUS DATETIME"
Obviously you'd need to replace my quoted strings with code which returned the date and datetime of interest. If the headcount doesn't return to zero at midnight, you can achieve the same by removing the first line of the where clause.
I am using the Graph Reports for the select below. The MySQL database only has the active records in the database, so if no records are in the database from X hours till Y hours that select does not return anything. So in my case, I need that select return Paypal zero values as well even the no activity was in the database. And I do not understand how to use the UNION function or re-create select in order to get the zero values if nothing was recorded in the database in time interval. Could you please help?
select STR_TO_DATE ( DATE_FORMAT(`acctstarttime`,'%y-%m-%d %H'),'%y-%m-%d %H')
as '#date', count(*) as `Active Paid Accounts`
from radacct_history where `paymentmethod` = 'PayPal'
group by DATE_FORMAT(`#date`,'%y-%m-%d %H')
When I run the select the output is:
Current Output
But I need if there are no values between 2016-07-27 07:00:00 and 2016-07-28 11:00:00, then in every hour it should show zero active accounts Like that:
Needed output with no values every hour
I have created such select below , but it not put to every hour the zero value like i need. showing the big gap between the 12 Sep and 13 Sep anyway, but there should be the zero values every hour
(select STR_TO_DATE ( DATE_FORMAT(acctstarttime,'%y-%m-%d %H'),'%y-%m-%d %H')
as '#date', count(paymentmethod) as Active Paid Accounts
from radacct_history where paymentmethod <> 'PayPal'
group by DATE_FORMAT(#date,'%y-%m-%d %H'))
union ALL
(select STR_TO_DATE ( DATE_FORMAT(acctstarttime,'%y-%m-%d %H'),'%y-%m-%d %H')
as '#date', 0 as Active Paid Accounts
from radacct_history where paymentmethod <> 'PayPal'
group by DATE_FORMAT(#date,'%y-%m-%d %H')) ;
I guess, you want to return 0 if there is no matching rows in MySQL. Here is an example:
(SELECT Col1,Col2,Col3 FROM ExampleTable WHERE ID='1234')
UNION (SELECT 'Def Val' AS Col1,'none' AS Col2,'' AS Col3) LIMIT 1;
Updated the post: You are trying to retrieve data that aren't present in the table, I guess in reference to the output provided. So in this case, you have to maintain a date table to show the date that aren't in the table. Please refer to this and it's little bit tricky - SQL query that returns all dates not used in a table
You need an artificial table with all necessary time intervals. E.g. if you need daily data create a table and add all day dates e.g. start from 1970 till 2100.
Then you can use the table and LEFT JOIN your radacct_history. So for each desired interval you will have group item (group by should be based on the intervals table.
We have a statistics database of which we would like to group some results. Every entry has a timestamp 'tstarted'.
We would like to group by every quarter of the day. For each quarter, we would like to know the day count where we have > 0 results (for that quarter).
We could resolve this by using a subquery:
select quarter, sum(q), count(quarter), sum(q) / count(quarter) as average
from (
select SEC_TO_TIME((TIME_TO_SEC(tstarted) DIV 900) * 900) as quarter, sum(qdelivered) as q
from statistics
where stat_field = 1
group by SEC_TO_TIME((TIME_TO_SEC(tstarted) DIV 900) * 900), date(tstarted)
order by SEC_TO_TIME((TIME_TO_SEC(tstarted) DIV 900) * 900) asc
) as sub
group by quarter
My question: is there a more efficient way to retrieve this result (e.g. join or other way)?
Efficiency could be improved by eliminating the inline view (derived table aliased as sub), and doing all the work in a single query. (This is because of the way that MySQL processes the inline view, creating and populating a temporary MyISAM table.)
I don't understand why the expression date(tstarted) needs to be included in the GROUP BY clause; I don't see that removing that would change the result set returned by the query.
I do now see the effect of including the date(tstarted) in the GROUP BY of the inline view query.
I think this query returns the same result as the original:
SELECT SEC_TO_TIME((TIME_TO_SEC(s.tstarted) DIV 900) * 900) AS `quarter`
, SUM(s.qdelivered) AS `q`
, COUNT(DISTINCT DATE(s.tstarted)) AS `day_count`
, SUM(s.qdelivered) / COUNT(DISTINCT DATE(s.tstarted)) AS `average`
FROM statistics s
WHERE s.stat_field = 1
GROUP BY SEC_TO_TIME((TIME_TO_SEC(s.tstarted) DIV 900) * 900)
This should be more efficient since it avoids materializing an intermediate derived table.
Your question said you wanted a "day count"; that sounds like you want a count of the each day that had a row within a particular quarter hour.
To get that, you could just add an aggregate expression to the SELECT list,
, COUNT(DISTINCT DATE(s.tstarted)) AS `day_count`
I would be tempted to set up a table of quarters in the day. Use this table and LEFT JOIN your statistics table it.
CREATE TABLE quarters
(
id INT,
start_qtr INT,
end_qtr INT
);
INSERT INTO quarters (id, start_qtr, end_qtr) VALUES
(1,0,899),
(2,900,1799),
(3,1800,2699),
(4,2700,3599),
(5,3600,4499),
(6,4500,5399),
(7,5400,6299),
(8,6300,7199),
etc;
Your query can then be:-
SELECT SEC_TO_TIME(quarters.start_qtr) AS quarter,
sum(statistics.qdelivered),
count(statistics.qdelivered),
sum(statistics.qdelivered) / count(statistics.qdelivered) as average
FROM quarters
LEFT OUTER JOIN statistics
ON TIME_TO_SEC(statistics.tstarted) BETWEEN quarters.start_qtr AND quarters.end_qtr
AND statistics.stat_field = 1
AND DATE(statistics.tstarted) = '2014-06-30'
GROUP BY quarter
ORDER BY quarter;
Advantage of this is that it will give you entries with a count of 0 (and an average of NULL) for quarters where there are no statistics, and it saves some of the calculations.
You could save more calculations by adding time columns to the quarters table:-
CREATE TABLE quarters
(
id INT,
start_qtr INT,
end_qtr INT
start_qtr_time TIME,
end_qtr_time TIME,
);
INSERT INTO quarters (id, start_qtr, end_qtr, start_qtr_time, end_qtr_time) VALUES
(1,0,899, '00:00:00', '00:14:59'),
(2,900,1799, '00:15:00', '00:29:59'),
(3,1800,2699, '00:30:00', '00:44:59'),
(4,2700,3599, '00:45:00', '00:59:59'),
(5,3600,4499, '01:00:00', '01:14:59'),
(6,4500,5399, '01:15:00', '01:29:59'),
(7,5400,6299, '01:30:00', '01:44:59'),
(8,6300,7199, '01:45:00', '01:59:59'),
etc
Then this saves the use of a function on the JOIN:-
SELECT start_qtr_time AS quarter,
sum(statistics.qdelivered),
count(statistics.qdelivered),
sum(statistics.qdelivered) / count(statistics.qdelivered) as average
FROM quarters
LEFT OUTER JOIN statistics
ON TIME(statistics.tstarted) BETWEEN quarters.start_qtr_time AND quarters.end_qtr_time
AND statistics.stat_field = 1
AND DATE(statistics.tstarted) = '2014-06-30'
GROUP BY quarter
ORDER BY quarter;
These both assume you are interested in a particular day.