select ansidate(xxx) + '3 months' AS date1
from (
select str_to_date(varchar(max_date),'%Y%m%d') as xxx
from comp_stg_rundate
where row_key = 1
)as s
Max_date is saved as an interger in the comp_stg_rundate table, I want to add 3 months onto this date. The fuction DateAdd won't work as I am using VectorWise.
Ok, I don't know VectorWise or how ansidate is stored, however, if it's stored as an integer value I assume it represents a certain amount of time, measured on a specific time unit since a starting time point.
If it's true, you can convert your 3 months to the time unit in which ansidate is being stored and add the converted value.
What version of Vectorwise did you run this against because it works for me on VW 4.0.
However this also works.
timestampadd(MONTH,3,ansidate(xxx))
Related
Scenario
A user selects a date. Based on the selection I check whether the date & time is booked or not (No issues here).
If a date & time is booked, I need to show them n alternative dates. Based on their date and time parameters, and those proposed alternative dates have to be as close as to their chosen date as possible. The list of alternative dates should start from the date the query is ran on My backend handles this.
My Progress So Far
SELECT alternative_date
FROM GENERATE_SERIES(
TIMESTAMP '2022-08-20 05:00:00',
date_trunc('month', TIMESTAMP '2022-08-20 07:00:00') + INTERVAL '1 month - 1 day',
INTERVAL '1 day'
) AS G(alternative_date)
WHERE NOT EXISTS(
SELECT * FROM events T
WHERE T.bookDate::DATE = G.alternative_date::DATE
)
The code above uses the GENERATE_SERIES(...) function in PSQL. It searches for all dates, starting from 2022-08-20, and up to the end of August. It specifically returns the dates which does not exist in the bookDate column (Meaning it has not yet been booked).
Problems I Need Help With
When searching for alternative dates, I'm providing 3 important things
The user's preferred booking date, so I can suggest which other dates are close to him that he can choose? How would I go about doing this? It's the part where I'm facing most trouble.
The user's start and end times, so when providing a list of alternative dates, I can tell him, hey there's free space between 06 and 07 on the date 2022-08-22 for instance. I'm also facing some issues here, a push in the right track will be great!
I want to add another WHERE but it fails, the current WHERE is a NOT EXISTS so it looks for all dates not equaling to what is given. My other WHERE basically means WHERE the place is open for booking or not.
To get closest free dates, you can ORDER BY your result by "distance" of particular alternative date to user's preferred date - the shortest intervals will be first:
ORDER BY alternative_date - TIMESTAMP '2022-08-20 05:00:00'
If you want to recommend time slots smaller than whole dates (hour range), you need to switch the whole thing from dates to hours, i.e. generate_series from 1 day to 1 hour (or whatever your smallest bookable unit is) and excluse invalid hours (nighttime I assume) in WHERE. From there, it is pretty much the same as with dates.
As for "second where", there can be only one WHERE, but it can be composed from multiple conditions - you can add more conditions using AND operator (and it can also be sub-query if needed):
WHERE NOT EXISTS(
SELECT * FROM events T
WHERE T.bookDate::DATE = G.alternative_date::DATE
) AND NOT EXISTS (
SELECT 1 FROM events WHERE "roomId" = '13b46460-162d-4d32-94c0-e27dd9246c79'
)
(warning: this second sub-query is probably dangerous in real world, since the room will be used more than one time, I assume, so you need to add some time condition to the subquery to check against date)
Let's assume that we have the following input parameters:
date [Date]
period [Integer]
The task is the following: build the table which has two columns: date and dayname.
So, if we have date = 2018-07-12 and period = 3 the table should look like this:
date |dayname
-------------------
2018-07-12|THURSDAY
2018-07-13|FRIDAY
2018-07-14|SATURDAY
My solution is the following:
select add_days(date, -1) into previousDay from "DUMMY";
for i in 1..:period do
select add_days(previousDay, i) into nextDay from "DUMMY";
:result.insert((nextDay, dayname(nextDay));
end for;
but I don't like the loop. I assume that it might be a problem in the performance if there are more complicated values that I want to put to result table.
What would be the better solution to achieve the target?
Running through a loop and inserting values one by one is most certainly the slowest possible option to accomplish the task.
Instead, you could use SAP HANA's time series feature.
With a statement like
SELECT to_date(GENERATED_PERIOD_START)
FROM SERIES_GENERATE_TIMESTAMP('INTERVAL 1 DAY', '01.01.0001', '31.12.9999')
you could generate a bounded range of valid dates with a given interval length.
In my tests using this approach brought the time to insert a set of dates from ca. 9 minutes down to 7 seconds...
I've written about that some time ago here and here if you want some more examples for that.
In those examples, I even included the use of series tables that allow for efficient compression of timestamp column values.
Series Data functions include SERIES_GENERATE_DATE which returns a set of values in date data format. So you don't have to bother to convert returned data into desired date format.
Here is a sample code
declare d int := 5;
declare dstart date := '01.01.2018';
SELECT generated_period_start FROM SERIES_GENERATE_DATE('INTERVAL 1 DAY', :dstart, add_days(:dstart, :d));
I'm looking to calculate how many days have passed since a specific date, retrieved from a table in my database. Based on the info I've found on W3Schools (Here), I have attempted using DATEDIFF, but am coming up against a couple of different errors I can't seem to work around.
I have included my code below, and based on this, what I want to happen is this: Select the "DD" from the "Wave_Data" table, and, based on "sysdate", work out how many days have lapsed since then.
SELECT DATEDIFF(WEEKDAY,:P1_DD,SYSDATE)
FROM WAVE_DATA
WHERE WAVE_NUMBER = :P1_WAVE;
The final calculation would then be inputted into a text field within my ApEx database.
Thank you in advance for any help you may be able to provide,
Dominic
In Oracle you can just subtract one Date from another to get the difference (in days) between them:
SELECT SYSDATE - :p1_dd
FROM Wave_Data
WHERE Wave_Number = :p1_wave;
If you want to know the difference between the dates without any time parts then you can do:
SELECT TRUNC( SYSDATE ) - TRUNC( :p1_dd )
FROM Wave_Data
WHERE Wave_Number = :p1_wave;
or
SELECT FLOOR( SYSDATE - :p1_dd )
FROM Wave_Data
WHERE Wave_Number = :p1_wave;
suppose I have a table MyTable with a column some_date (date type of course) and I want to select the newest 3 months data (or x days).
What is the best way to achieve this?
Please notice that the date should not be measured from today but rather from the date range in the table (which might be older then today)
I need to find the maximum date and compare it to each row - if the difference is less than x days, return it.
All of this should be done with sqlalchemy and without loading the entire table.
What is the best way of doing it? must I have a subquery to find the maximum date? How do I select last X days?
Any help is appreciated.
EDIT:
The following query works in Oracle but seems inefficient (is max calculated for each row?) and I don't think that it'll work for all dialects:
select * from my_table where (select max(some_date) from my_table) - some_date < 10
You can do this in a single query and without resorting to creating datediff.
Here is an example I used for getting everything in the past day:
one_day = timedelta(hours=24)
one_day_ago = datetime.now() - one_day
Message.query.filter(Message.created > one_day_ago).all()
You can adapt the timedelta to whatever time range you are interested in.
UPDATE
Upon re-reading your question it looks like I failed to take into account the fact that you want to compare two dates which are in the database rather than today's day. I'm pretty sure that this sort of behavior is going to be database specific. In Postgres, you can use straightforward arithmetic.
Operations with DATEs
1. The difference between two DATES is always an INTEGER, representing the number of DAYS difference
DATE '1999-12-30' - DATE '1999-12-11' = INTEGER 19
You may add or subtract an INTEGER to a DATE to produce another DATE
DATE '1999-12-11' + INTEGER 19 = DATE '1999-12-30'
You're probably using timestamps if you are storing dates in postgres. Doing math with timestamps produces an interval object. Sqlalachemy works with timedeltas as a representation of intervals. So you could do something like:
one_day = timedelta(hours=24)
Model.query.join(ModelB, Model.created - ModelB.created < interval)
I haven't tested this exactly, but I've done things like this and they have worked.
I ended up doing two selects - one to get the max date and another to get the data
using the datediff recipe from this thread I added a datediff function and using the query q = session.query(MyTable).filter(datediff(max_date, some_date) < 10)
I still don't think this is the best way, but untill someone proves me wrong, it will have to do...
So I've got a task that takes a random 20% of a table's results from the previous day to use as a control group. These results are put into a table, and then shoved into a .CSV file for use by the employer.
That works perfectly well. The only problem is, it's in a group of tasks that are often tested, which means that when the task gets repeated, more random data gets dumped into the file - meaning manual deletion of rows. I'm looking for a fix.
Because the process is run once a day, a unique key is the TransactionDateID, formatted INT (20150603). I need to check against that column to make sure that nothing has been run on that same day. The problem is exacerbated because it involves yesterday's records.
For example. In order to check todays date to see if it has been run, getDate() would be used to get today's date, then converted to INT (20150604). But I can't simply check to see if there is a numerical difference of 1, because once the month switches, a simple +1 will throw the entire thing out of whack:
(20150631) + 1 =/= (20150701)
I'm just wondering if this is going to be casting/converting back and forth because of the difference in variable types, or if there's something I can do with a BIT to add a column if the task has been completed for the day, something along those lines.
A colleague suggested using MAX(TransactionDateID) and then checking getDate() against that column.
Unfortunately, I run into a problem the following day:
Initial task run at 2015-06-04-09:30:ss:mm
2015-06-04-11:45:ss:mm etc.. > 2015-06-04-09:30:ss:mm, DO NOT RUN
2015-06-05-09:30:ss:mm etc.. > 2015-06-04-09:30:ss:mm, I want it to run ...
To convert your day to a formatted int, try this:
DECLARE #today date = getdate()
select year(#today) * 10000 + month(#today) * 100 + day(#today)