How do I perform an equivalent of SQL extract/fetch records by month and year from a date in swift?
Two requirements are as follows:
List records by Month and Year
September 2015
October 2015
Display transactions falling under the Year and Month.
Edit: I do mean core data. Rephrased "equivalent in SQL" to equivalent of SQL" to clarify.
CoreData will store dates as doubles, which is the internal format for NSDate.
If you have a small database, just store the values as NSDate and filter based on that.
However, if you have a large database, you may want to denormalize your data a bit more.
You could store another field, say in "yyyymmdd" format, which gives you most of the filtering you require.
For finer grained control, you can also keep separate attributes for year, month, and day.
You may want to setup those fields as indexes as well, if you do lots of searching over vast amounts of data.
Remember, CoreData uses SQLite under the hood for most databases, but it's behavior characteristics are very different.
There is no universal "best" way, as it depends entirely on your data and how you use it.
Related
Good day all,
I am trying to filter todays result in SQL table to a collection in powerapps. The column "dt" represents the column in sql of datetime type.
This is my powerapps filter:
ClearCollect(myCollectionName, Filter(myDatasource, Text(dt,"dd/mm/yyyy") = Text(Now(),"dd/mm/yyyy" )));
Seems like the collection is still empty even there is data for today in sql. May I know if my approach is the correct way in filtering?
Short answer: the data is likely being changed based on the client time zone. To fix it, you can update it by applying the time zone offset to the data from the SQL table, something along the lines of:
ClearCollect(
myCollectionName,
Filter(
myDatasource,
Text(DateAdd(dt, TimeZoneOffset(dt), Minutes), "dd/mm/yyyy") =
Text(Now(), "dd/mm/yyyy")))
Long(er) answer: the datetime type in SQL Server represents an absolute value of date and time. For example, the value '2021-12-23 09:30:00' represents 9:30 in the morning of the 23rd day of December, 2021 - at any part of the world. The date/time type in Power Apps, however, represents a point in time, typically referring to the local time where the app is being executed (or created). For example, if I selected that value and I'm in the US Pacific Time Zone (UTC-08:00), that would represent the same value as if someone in London (UTC+00:00) selected 2021-12-23 17:30:00. Since the two types represent different concepts, we may have mismatches like you are facing. To fix this, we can either use a type in SQL Server that has the same semantics as Power Apps (for example, 'datetimeoffset'), or adjust the time when it is being transferred between SQL and Power Apps.
The blog post at https://powerapps.microsoft.com/en-us/blog/working-with-datetime-values-in-sql explains in more details how to work with date/time values in SQL and Power Apps.
Let's say I have a date dimension and from my business requirements I know that the most granular I would need to go is to examine the specific day of the month that an event occurred.
The data I am given provides me with the exact time that an event occurred (YYYY-MM-DD HH:MM:SS). I have two opitons:
Before loading the data into the date dimension, slice the HH:MM:SS from the date.
Create the time attributes in my date dimension and insert the full date time.
The way I see it, I should go with the option 1. This would remove redundant data and save some space. However, if I go with option 2, should the business requirements ever change or if my manager suddenly wants to be more granular I wouldn't need to modify my original design. Which option is more commonly used? Are there more options that I did not consider?
Update - follow up question
I receive new data every month. If I used a pre built date dimension with all the dates would I then need to run my script every month to populate the table with new dates of that month or would I have a continuous process where by every day insert into the table one row, which would be that date?
I would agree with you and avoid option 2. A standard date dimension table is at the individual date level. If you did need to analyse by time of day, you could create an additional time of day dimension at the level of a second in a single day, and link to that from your fact table.
Your date dimension should be created by script automatically, rather than from the dates that events occurred. This allows you to analyse across a range of events from other facts, and on dates where no events occur, using a standard, prebuilt dimension.
I would also include the full date/time stamp as a column in the fact table, along with the 'DateKey' to the dimension table. This would allow you some visibility/analysis of the timestamp, you would not lose the data, and would still allow you to analyse by the date dimension.
Update - follow up question
Your pre-built date dimension (the standard way of doing it) would usually contain some dates in the future. There's no reason not to, for example, include another 5 years of dates in the table. But if you'd like it to gradually grow over time, you could have a script that is run once a day, once a month, or once a year to add new dates. Its totally up to you! There are many example scripts for building date dimensions- just google date dimension script. They exist for the language of your choice, e.g. SQL, C#, Power Query, etc.
I'm an historian of medieval history and I'm trying to code networks between kings, dukes, popes etc. over a period of time of about 50 years (from 1220 to 1270) in medieval Germany. As I'm not a specialist for graph-databases I'm looking for a possibility to handle dates and date-ranges.
Are there any possibilities to handle over a date-range to an edge so that the edges, which represents a relationship, disappears after e.g. 3 years?
Are there any possibility to ask for relationships who have their date-tag in a date-range?
The common way to deal with dates in Neo4j is storing them either as a string representation or as millis since epoch (aka msec passed since Jan 01 1970).
The first approach makes the graph more easily readable the latter allows you to do math e.g. calculate deltas.
In your case I'd store two properties called validFrom and validTo on the relationships. You queries need to make sure you're looking for the correct time interval.
E.g. to find the king(s) in charge of France from Jan 01 1220 to Dec 31st 1221 you do:
MATCH (c:Country{name:'France'})-[r:HAS_KING]->(king)
WHERE r.validFrom >= -23667123600000 and r.validTo <=-23604051600000
RETURN king, r.validFrom, r.validTo
addendum
Since Neo4j 3.0 there's the APOC library which provides couple of functions for converting timestamps to/from human readable date strings.
You can also store the dates in their number representation in the following format: YYYYMMDD
In your case 12200101 would be Jan 1st 1220 and 12701231 would be Dec 31st 1270.
It's a useful and readable format and you can perform range searches like:
MATCH (h:HistoricEvent)
WHERE h.date >= 12200101 AND h.date < 12701231
RETURN h
It would also let you order by dates, if you need to.
As of Neo4J 3.4, the system handles duration and dates, see the official documentation. See more examples here.
An example related to the original question: Retrieve the historical events that happened in the last 30 days from now :
WITH duration({days: 30}) AS duration
MATCH (h:HistoricEvent)
WHERE date() - duration < date(h.date)
RETURN h
Another option for dates that keeps the number of nodes/properties you create fairly low is a linked list years (earliest year of interest - latest year), one of months (1-12), and one of dates in a month (1-31). Then every "event" in your graph can be connected to a year, month, and day. This way you don't have to create a new node for every new combination of a year month and day. You just have a single set of months, one of days, and one year. I scale the numbers to make manipulating them easier like so
Years are yyyy*10000
Months are mm*100
Date are dd
so if you run a query such as
match (event)-[:happened]->(t:time)
with event,sum(t.num) as date
return event.name,date
order by date
You will get a list of all events in chronological order with dates like Janurary 17th, 1904 appearing as 19040117 (yyyymmdd format)
Further, since these are linked lists where, for example,
...-(t0:time {num:19040000})-[:precedes]->(t1:time {num:19050000})-...
ordering is built into the nodes too.
This is, so far, how I have liked to do my event dating
One of my customers would like to have a custom date column, where he could store the year only, a combination of month and year (without the day), or a classic date with day, month and year.
It should be possible to use this field for sorting the data. A "month-year" date should be considered as "01-month-year" for the sort, and a "year" date should be treated as "01-01-year" for the sort.
I could imagine two solutions to that:
Store the date in the standard "day-month-year" format, and keep in a separate column how the date was entered ("year", "month-year", "day-month-year"), so the approximate date can be displayed exactly how it was entered.
Use some sort of custom date column in the postgresql database.
Has anyone experience with that?
You could use date-time functions to extract date components. I don't think it has any sense to create additional columns. Also, some databases allow to create indexes by functions.
In my application I have to store data month wise and year wise. So for this, I have to store the data along with date into database.
My requirement is how to store in terms of date and how to retrieve data with group by month and year. In my app I am showing a table of years and months, based on selected month and year. I have to show the data in a dashboard.
My problem is in storing and retrieving date data types.
Use the following syntax
SELECT * FROM DATABASE WHERE REQUIREDDATEFIELD LIKE '%2011-01%';
2011 is supposed to be the year
01 is supposed to be the month
DATABASE is supposed to be your mysql database name
REQUIREDDATEFIELD is supposed to be the field you are hoping to sort from month and year.
like '%2011-01%' is supposed to be meaning, all the records containing 2011-01 in the given field. It could be in the beginning or the end or in the middle of a large text, so having % in both the beginning and end of the search criteria is a good habit.
You just select either for a specific month or year or month and year. Or if you want all, you use GROUP BY.
I know this answer is quite vague and generic, but that's because your question is vague. You probably need to be more specific. Explain not only what you want to do, but what you have tried, and in which way that didn't work.