I got a table which tracks positions over time. This table contains a lot of rows and cannot be changed in format.
Every position is inserted with an id, the actual position and a timestamp (datetime). The position itself is inserted in a concatenated string which can be converted to x/y coordinates using custom functions.
I want to create a procedure, and lists all known positions and their appropiate timestamps for a certain. No problem so far. But also want to create an output column which indicates the difference in position and time.
To clarify. What I have:
Id | Timestamp | Foreign_Id | POS
----------------------------------------------------------
1 | 2011-02-20 00:00:00 | 2 | PositionAsString
----------------------------------------------------------
2 | 2011-02-20 00:00:05 | 2 | PositionAsString
----------------------------------------------------------
3 | 2011-02-20 00:00:15 | 2 | PositionAsString
----------------------------------------------------------
4 | 2011-02-20 00:00:37 | 2 | PositionAsString
The Coordinates of the Position are available via the functions getX and getY which return float values for X and Y.
The difference in position would be calculated using the Pythagorean theorem as it is only 2D.
What I want
Id | Timestamp | Foreign_Id | POS | DiffPos | Speed
---------------------------------------------------------------------------
1 | 2011-02-20 00:00:00 | 2 | PositionAsString | 0 | 0
---------------------------------------------------------------------------
2 | 2011-02-20 00:00:05 | 2 | PositionAsString | 20 | 4
---------------------------------------------------------------------------
3 | 2011-02-20 00:00:10 | 2 | PositionAsString | 10 | 2
---------------------------------------------------------------------------
4 | 2011-02-20 00:00:20 | 2 | PositionAsString | 10 | 1
So now my issue is how to calculate the difference to the previous row.
Important is, that the result set is narrowed down to the foreign key befor any unefficient calculations are performed because the table has many rows.
Thanks for the suggestion, however as this is complicated and inefficient I am now using another solution. As I stated above I am unable to change the format of the source table. But what is possible was to modify the trigger which was writing to this tracking table so that it did compute the differences before inserting the new row.
This will of course not work for existing entries but this is acceptable.
Related
I'm creating a database (in MySQL) with a table of measurements. For each measurement I want to store the DateTime it came in. For showing plots within an app for different intervals (measurements of the day/week/month/year) I want sample the data points I have, so I can return e. g. 30 data points for the whole year as well as for the day/hour. This is the same as done with stock price graphs:
stock price plot for 1 day
vs
stock price plot for 1 month
As you can see, the amount of data points is the same in both pictures.
So how can I select x entries within a timespan in MySQL via SQL?
My data looks like this:
+====+====================+=============+==========+
| id | datetime | temperature | humidity |
+====+====================+=============+==========+
| 1 | 1-15-2016 00:30:00 | 20 | 40 |
+----+--------------------+-------------+----------+
| 2 | 1-15-2016 00:35:00 | 19 | 41 |
+----+--------------------+-------------+----------+
| 3 | 1-15-2016 00:40:00 | 20 | 40 |
+----+--------------------+-------------+----------+
| 4 | 1-15-2016 00:45:00 | 20 | 42 |
+----+--------------------+-------------+----------+
| 5 | 1-15-2016 00:50:00 | 21 | 42 |
+----+--------------------+-------------+----------+
| 6 | 1-15-2016 00:55:00 | 20 | 43 |
+----+--------------------+-------------+----------+
| 7 | 1-15-2016 01:00:00 | 21 | 43 |
+====+====================+=============+==========+
Let's say, I always want two data points (in reality a lot more). So for the last half hour I want the database to return data point 1 and 4, for the last ten minutes I want it to return 6 and 7.
Thanks for helping!
PS: I'm sorry for any errors in my English
OK, assuming a very simple systematic approach, you can get the first and last entry for any defined period:
select *
from table
where mydatetime =
(select
max(mydatetime)
from table
where mydatetime between '2017-03-01' and '2017-03-15'
)
OR mydatetime =
(select
min(mydatetime)
from table
where mydatetime between '2017-03-01' and '2017-03-15'
)
I believe your answer can be found at the following location:
https://stackoverflow.com/a/1891796/7176046
If you are looking to filter out any items not within your date/time your query would use:
Select * from table where Date/Time is (What you want to sort by)
For ex.: The process of buy a rice bag of 100 kg, give one entry for the completely bag, and then give out 20 or 30 kilogram of that bag. How to achieve it in the stock database.
The structure can be different based on the behaviour of your application. There is no absolute way. But, I give you an example and you can find an idea:
inventory table:
id
date
merchandise_id
amount (negative for exit and positive for entry)
inventory_id (this is null for entry and includes the id of entry for exits)
Sample data:
id | date | merchandise_id | amount | inventory_id
-----------------------------------------------------------------
1 | 2016-06-01 | 32 | 100 | NULL
2 | 2016-06-03 | 32 | -20 | 1
3 | 2016-06-04 | 32 | -30 | 1
I have one table having 5 columns
linkid, orinodeno, orinodeno, ternodeno, terifindex
linkid is autoincremented. orinodeno, oriifindex is one combination value and ternodeno, terifindex other combination (orinodeno,oriifindex is originating value and ternodeno,terifindex terminating value i.e, in between there is a link eg just like map two pts n in between connecting link) so my table contains a->b values (i.e a is combination of orinodeno, oriifindex and b is combination of ternodeno,terifindex) and b->a values. so I have to select only a->b set of values not b->a. Also sending my table image. My Table
There is no a map definition in sql databases, forget it. Check any database normalization tutorial. Then you shouldn't have any problems with select statements.
Please be clear about what you are asking. If you can not explain in words, please give example input and your expected output.
From link of table image you have provided and description, It looks like you expect following:
Data in current table:
------------------------------------------------------------------
|linkid | orinodenumber | oriifindex | ternodenumber | terifindex|
------------------------------------------------------------------
|305 | 261 | 2 | 309 | 2 |
|306 | 309 | 2 | 261 | 2 |
|307 | 257 | 10 | 310 | 10 |
|308 | 310 | 10 | 257 | 10 |
|309 | 257 | 11 | 310 | 11 |
------------------------------------------------------------------
Expected Output:
------------------------------------------------------------------
|linkid | orinodenumber | oriifindex | ternodenumber | terifindex|
------------------------------------------------------------------
|305 | 261 | 2 | 309 | 2 |
|307 | 257 | 10 | 310 | 10 |
------------------------------------------------------------------
If that is your case, following query might help you (Assuming table name as link_table):
SELECT *
FROM link_table o
WHERE EXISTS (SELECT linkid
FROM link_table i
WHERE o.orinodenumber = i.ternodenumber
AND o.oriifindex = i.terifindex
AND o.linkid < i.linkid);
I have a 'Course' table and an 'Event' table.
I would like to have all the courses that actually take place, i.e. they are not cancelled by an event.
I have done this by a simple request for all the course and a script analysis (basically some loops), but this request take a time that I believe too long. I think what I want is possible in one query and no loops to optimize this request.
Here are the details :
'Course' c have the fields 'date', 'duration' and a many to many relation with the 'Grade' table
'Event' e have the fields 'begin', 'end', 'break' and a many to many relation with the 'Grade' table
A course is cancelled by an event if they occur at the same time and if the event is a break (e.break = 1)
A course is cancelled by an event if all the grades of the course are in the events that occurs at the same time (many events can occurs, I have to sum up the grades of these events and compare them to the grades of the courses). This is the part I'm doing with a loop, I have some trouble to conceptualize that.
Any help is welcome,
Thanks in advance,
PS : I'm using mysql
EDIT : Tables details
-Course
+-----------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| date | datetime | NO | | NULL | |
| duration | time | NO | | NULL | |
| type | int(11) | NO | | NULL | |
+-----------+-------------+------+-----+---------+----------------+
+-------+---------------------+----------+------+
| id | date | duration | type |
+-------+---------------------+----------+------+
| 1 | 2013-12-10 10:00:00 | 02:00:00 | 0 |
| 2 | 2013-12-11 10:00:00 | 02:00:00 | 0 |
+-------+---------------------+----------+------+
-Event
+-------------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| begin | datetime | NO | | NULL | |
| end | datetime | YES | | NULL | |
| break | tinyint(1) | NO | | NULL | |
+-------------+-------------+------+-----+---------+----------------+
+----+---------------------+---------------------+-------+
| id | begin | end | break |
+----+---------------------+---------------------+-------+
| 1 | 2013-12-10 00:00:00 | 2013-12-11 23:59:00 | 1 |
+----+---------------------+---------------------+-------+
-course_grade
+-----------+----------+
| course_id | grade_id |
+-----------+----------+
| 1 | 66 |
| 2 | 65 |
| 2 | 66 |
+-----------+----------+
-event_grade
+----------+----------+
| grade_id | event_id |
+----------+----------+
| 66 | 1 |
+----------+----------+
So here, only the course 2 should appear, because course 1 has only one grade, and this grade has an event.
I like riddles, this is a nice one, has many solutions, I think
As you say 'Any help is welcome', I give an answer altough its not the solution (and it does not fit into a comment)
I dont know, if you just want (A) the naked statement (over and out), or if you want (B) to understand how to get to the solution, I take (B)
I start with 'what would I change' before starting about the solution:
you are mixing date,datetime,start,end and duration, try to use only one logic (if it is your model ofcourse) ie.
an event/course has a start and an end time (or start/duration)
duration should (IMHO) not be a time
try to find a smallest timeslice for events/course (are there 1 sec events? or is a granularity of 5' (ie. 10:00, 10:05, 10:10 ans so on) a valid compromise?
My solution, a prgmatic one not academic
(sounds funny, but does work good in a simillar prob I had see annotation)
Create a table (T_TIME_OF_DAY) having all from 00:00, 00:05, .. 23:55
Create a Table (T_DAYS) in a valid and usefull range (a year?)
the carthesian product - call it points in time - (ie. select date, time from T_DAYS,T_TIME_OF_DAY no condition) of them (days x times) 300*24*12 ~ 100.000 rows if you need to look at a whole year (and 5' are ok for you) - thats not much and no prob
the next step is to join the curses fitting to your points in time (and the rows are down to <<100.000)
if you next join these with your events (again using point in time) you should get what you want.
simplyfied quarters of a day:
12 12 12 12 12 12 12 12
08 09 10 11 12 13 14 15
|...|...|...|...|...|...|...|...
grade 65 (C).............2..................
grade 66 (C).........1...2..................
grade 65 (E)................................
grade 66 (e)........1111..................
(annotation: I use this logic to calculate the availabillity of services regarding to their downtimes per Month / Year, and could use the already in timeslices prepared data for display)
(second answer, because it is a totaly different and mor3 standard aproach)
I made an SQLFiddle for you
so what to do:
and thats the a solution:
step one (in mind) select course,grades (lets call them C)
step two (in mind) select events, grades (lets call them E)
and - tada -
select all from C where there a no rows in E that have the same grade and the same date(somehow) and eventtype='break'
so your solution:
select
id, date start_time, date+duration end_time, grade_id
from Course c join course_grade cg on c.id=cg.course_id
where not exists (
select grade_id, begin start_time, end end_time
from event_grade eg join event e on eg.event_id=e.id
where
eg.grade_id=cg.grade_id
and e.break=1
and
(
(e.begin<=c.date and e.end >=c.date+c.duration)
or e.begin between c.date and c.date+c.duration
or e.end between c.date and c.date+c.duration
)
)
I did take no attention to optimize here
I have a table that stores nested sets. It stores different nested sets differentiated by a collectionid (yes i'm mixing terms here, really should be nestedsetid). it looks somewhat like this:
id | orgid | leftedge | rightedge | level | collectionid
1 | 123 | 1 | 6 | 1 | 1
2 | 111 | 2 | 3 | 2 | 1
3 | 23 | 4 | 5 | 2 | 1
4 | 67 | 1 | 2 | 1 | 2
5 | 123 | 3 | 4 | 1 | 2
6 | 600 | 1 | 6 | 1 | 3
7 | 11 | 2 | 5 | 2 | 3
8 | 111 | 3 | 4 | 3 | 3
Originally I wanted to take advantage of the R-Tree Indexes, but the code i have seen for this: LineString(Point(-1, leftedge), Point(1, rightedge)) won't quite work since it doesn't take into account the collectionid and this id:1 and id:6 would end up being the same.
Is there a way I can use the R-Tree index with my current set up... Surely you can have different nested sets in the same table? My main aim is to be able to use the MBRWithin and MBRContains functions. Using MySQL 5.1
For single-dimensional data (these are 1d intervals, right?) there exist better index structures than r-trees. These are designed for dynamic data in 2-10 dimensions (at higher dimensions, performance isn't too good, as the split strategies and distance functions don't work very well anymore)
Actually for your use case, classic SQL should work very well. And the database can make use of its indexes efficiently. Having a good index structure is one thing, but you want to have the database exploit the indexes it has as good as possible.
As such, I'd just index leftEdge and rightEdge and the <, <=, >, >= functions. They are fast! And for the collectionid column, a bitmap index should be good.