Set new year for date column in rails query - ruby-on-rails

I have the contract start of a number of companies, and I want to report on each contract year by creating a column with the contract start updated to a select year. There are a number of solutions in SQL involving functions like DATE_ADD or DATEFROMPARTS, but I'm having trouble adapting it to rails (if those functions are available at all).
The closest I've gotten is: Company.select("contract_start + '1 YEAR'::INTERVAL as new_contract_start"). This adds 1 year to each contract start but doesn't take into account contracts older than a year (or started the same year). I've also tried the following but again run into syntax errors:
new_year = 2020
Company.select("contract_start + '#{new_year} - EXTRACT (YEAR from contract_start) YEAR'::INTERVAL")
I'm looking for a solution that can either:
Directly set the year to what I want
Add a variable amount of years based on its distance from the desired year
I'm on Ruby 2.3.3

I think the key here was finding functions compatible with the PostgreSQL that my database was built on. Once I started searching for the functions I thought would help and their PostgreSQL equivalents, I found more compatible solutions, such as: NUMTODSINTERVAL in PostgreSQL
I ended up with:
contract_start_year = 2020
Company.select("contract_start + make_interval(years => CAST (#{contract_start_year} - EXTRACT (YEAR from contract_start) as INT))
I've also made it a bit smarter by adding the number of years required to get the latest contract date without going over the report date. This would be problematic if the report start date was "2020-01-01" but the contract start was "2017-06-01". Setting the contract date to "2020-06-01" would overshoot the intentions of the report.
report_start = "`2020-07-01`"
Company.select("contract_start + make_interval(years => CAST (EXTRACT (YEAR FROM AGE(CAST (#{start_quotations} AS DATE), contract_start)) AS INT)) as new_contract_year")
Note the additional single quotes in report_start since the SQL code need to read a string to convert it to a date
There might be other methods that can "build" the date directly, but this methods works well enough for now.

Related

Store the day of the week and time?

I have a two-part question about storing days of the week and time in a database. I'm using Rails 4.0, Ruby 2.0.0, and Postgres.
I have certain events, and those events have a schedule. For the event "Skydiving", for example, I might have Tuesday and Wednesday and 3 pm.
Is there a way for me to store the record for Tuesday and Wednesday in one row or should I have two records?
What is the best way to store the day and time? Is there a way to store day of week and time (not datetime) or should these be separate columns? If they should be separate, how would I store the day of the week? I was thinking of storing them as integer values, 0 for Sunday, 1 for Monday, since that's how the wday method for the Time class does it.
Any suggestions would be super helpful.
Is there a way for me to store the the record for Tuesday and
Wednesday in one row or do should I have two records?
There are several ways to store multiple time ranges in a single row. #bma already provided a couple of them. That might be useful to save disk space with very simple time patterns. The clean, flexible and "normalized" approach is to store one row per time range.
What is the best way to store the day and time?
Use a timestamp (or timestamptz if multiple time zones may be involved). Pick an arbitrary "staging" week and just ignore the date part while using the day and time aspect of the timestamp. Simplest and fastest in my experience, and all date and time related sanity-checks are built-in automatically. I use a range starting with 1996-01-01 00:00 for several similar applications for two reasons:
The first 7 days of the week coincide with the day of the month (for sun = 7).
It's the most recent leap year (providing Feb. 29 for yearly patterns) at the same time.
Range type
Since you are actually dealing with time ranges (not just "day and time") I suggest to use the built-in range type tsrange (or tstzrange). A major advantage: you can use the arsenal of built-in Range Functions and Operators. Requires Postgres 9.2 or later.
For instance, you can have an exclusion constraint building on that (implemented internally by way of a fully functional GiST index that may provide additional benefit), to rule out overlapping time ranges. Consider this related answer for details:
Preventing adjacent/overlapping entries with EXCLUDE in PostgreSQL
For this particular exclusion constraint (no overlapping ranges per event), you need to include the integer column event_id in the constraint, so you need to install the additional module btree_gist. Install once per database with:
CREATE EXTENSION btree_gist; -- once per db
Or you can have one simple CHECK constraint to restrict the allowed time period using the "range is contained by" operator <#.
Could look like this:
CREATE TABLE event (event_id serial PRIMARY KEY, ...);
CREATE TABLE schedule (
event_id integer NOT NULL REFERENCES event(event_id)
ON DELETE CASCADE ON UPDATE CASCADE
, t_range tsrange
, PRIMARY KEY (event_id, t_range)
, CHECK (t_range <# '[1996-01-01 00:00, 1996-01-09 00:00)') -- restrict period
, EXCLUDE USING gist (event_id WITH =, t_range WITH &&) -- disallow overlap
);
For a weekly schedule use the first seven days, Mon-Sun, or whatever suits you. Monthly or yearly schedules in a similar fashion.
How to extract day of week, time, etc?
#CDub provided a module to deal with it on the Ruby end. I can't comment on that, but you can do everything in Postgres as well, with impeccable performance.
SELECT ts::time AS t_time -- get the time (practically no cost)
SELECT EXTRACT(DOW FROM ts) AS dow -- get day of week (very cheap)
Or in similar fashion for range types:
SELECT EXTRACT(DOW FROM lower(t_range)) AS dow_from -- day of week lower bound
, EXTRACT(DOW FROM upper(t_range)) AS dow_to -- same for upper
, lower(t_range)::time AS time_from -- start time
, upper(t_range)::time AS time_to -- end time
FROM schedule;
db<>fiddle here
Old sqliddle
ISODOW instead of DOW for EXTRACT() returns 7 instead of 0 for sundays. There is a long list of what you can extract.
This related answer demonstrates how to use range type operator to compute a total duration for time ranges (last chapter):
Calculate working hours between 2 dates in PostgreSQL
Check out the ice_cube gem (link).
It can create a schedule object for you which you can persist to your database. You need not create two separate records. For the second part, you can create schedule based on any rule and you need not worry on how that will be saved in the database. You can use the methods provided by the gem to get whatever information you want from the persisted schedule object.
Depending how complex your scheduling needs are, you might want to have a look at RFC 5545, the iCalendar scheduling data format, for ideas on how to store the data.
If you needs are pretty simple, than that is probably overkill. Postgresql has many functions to convert date and time to whatever format you need.
For a simple way to store relative dates and times, you could store the day of week as an integer as you suggested, and the time as a TIME datatype. If you can have multiple days of the week that are valid, you might want to use an ARRAY.
Eg.
ARRAY[2,3]::INTEGER[] = Tues, Wed as Day of Week
'15:00:00'::TIME = 3pm
[EDIT: Add some simple examples]
/* Custom the time and timetz range types */
CREATE TYPE timerange AS RANGE (subtype = time);
--drop table if exists schedule;
create table schedule (
event_id integer not null, /* should be an FK to "events" table */
day_of_week integer[],
time_of_day time,
time_range timerange,
recurring text CHECK (recurring IN ('DAILY','WEEKLY','MONTHLY','YEARLY'))
);
insert into schedule (event_id, day_of_week, time_of_day, time_range, recurring)
values
(1, ARRAY[1,2,3,4,5]::INTEGER[], '15:00:00'::TIME, NULL, 'WEEKLY'),
(2, ARRAY[6,0]::INTEGER[], NULL, '(08:00:00,17:00:00]'::timerange, 'WEEKLY');
select * from schedule;
event_id | day_of_week | time_of_day | time_range | recurring
----------+-------------+-------------+---------------------+-----------
1 | {1,2,3,4,5} | 15:00:00 | | WEEKLY
2 | {6,0} | | (08:00:00,17:00:00] | WEEKLY
The first entry could be read as: the event is valid at 3pm Mon - Fri, with this schedule occurring every week.
The second entry could be read as: the event is valid Saturday and Sunday between 8am and 5pm, occurring every week.
The custom range type "timerange" is used to denote the lower and upper boundaries of your time range.
The '(' means "inclusive", and the trailing ']' means "exclusive", or in other words "greater than or equal to 8am and less than 5pm".
Why not just store the datestamp then use the built in functionality for Date to get the day of the week?
2.0.0p247 :139 > Date.today
=> Sun, 10 Nov 2013
2.0.0p247 :140 > Date.today.strftime("%A")
=> "Sunday"
strftime sounds like it can do everything for you. Here are the specific docs for it.
Specifically for what you're talking about, it sounds like you'd need an Event table that has_many :schedules, where a Schedule would have a start_date timestamp...

dynamic edge name creation using cypher query

START customerName=node(483), b = node(485, 498, 500)
MATCH customerName-[s:Sell]->b
WITH s.transactionDate AS date, customerName, b, sum(s.transactionAmount) AS total
CREATE customerName-[:sales_summary { date:date, tamt:total }]->b
Here I want to replace sales_summary relation into runtime date using MMM YY format.
like customerName - Sep 08 (tamt = total) -> b
here edge name = Sep 08 -- runtime value from date
Cypher does not have date manipulation methods in itself. You probably want to set the date on the relationship as a long, and then format MMM YY in your presentation code, which is much more performant in the database anyway.
I faced a similar challenge. For an SQL equivalent of TO_DATE(node.Date_value) > TO_DATE('01-JAN-09','DD-MON-YY') or something similar.
I guess currently we may have to go through the following steps:
a) Create nodes for Year Month, date using the code snippet provided here by Mark Needham.
b) Remember to make changes from MM-DD-YY (numerical) to DD-MON-YY inside the case conditions as per your data.
As Alan Robertson points out in the post comments, it is also an excellent way to understand neo4j functioning better for newbies like us even though it may require creating a few thousand nodes in the database which does not occupy much space.
This may not be an optimal answer, but may help to bail out from the immediate problem.
The best alternative is provided by Michael Hunger in here.
One of the ways to do it is to create an extra property which is unix epoch of the date and then divide the values by 86400 to get resolution of day. Thereafter, date manipulations can be done.

Rails. How to store time of day (for schedule)?

I'm writing an app that keeps track of school classes.
I need to store the schedule. For example: Monday-Friday from 8:am-11am.
I was thinking about using a simple string column but I'm going to need to make time calculations later.
For example, I need to store a representation of 8am, such as start_at:8am end_at:11am
So how should I store the time? What datatype should I use? Should I store start time and number of seconds or minutes and then calculate from there? or is there an easier way?
I use MySQL for production and SQLite for development.
I made an app recently that had to tackle this problem. I decided to store open_at and closed_at in seconds from midnight in a simple business hour model. ActiveSupport includes this handy helper for finding out the time in seconds since midnight:
Time.now.seconds_since_midnight
This way I can do a simple query to find out if a venue is open:
BusinessHour.where("open_at > ? and close_at < ?", Time.now.seconds_since_midnight, Time.now.seconds_since_midnight)
Any tips for making this better would be appreciated =)
If you're using Postgresql you can use a time column type which is just the time of day and no date. You can then query
Event.where("start_time > '10:00:00' and end_time < '12:00:00'")
Maybe MySQL has something similar
Check out the gem 'tod' for Rails 4 or Time_of_Day for Rails 3. They both solve the problem of storing time in a database while using an an Active Record model.
SQL has a time data type but Ruby does not. Active Record addresses this difference by representing time attributes using Ruby’s Time class on the canonical date 2000-01-01. All Time attributes are arbitrarily assigned the same dates. While the attributes can be compared with one another without an issue, (the dates are the same), errors arise when you attempt to compare them with other Time instances. Simply using Time.parse on a string like ”10:05” adds today’s date to the output.
Lailson Bandeira created a created solution for this problem, the Time_of_Day gem for Rails 3. Unfortunately the gem is no longer maintained. Use Jack Christensen’s ‘tod’ gem instead. It works like a charm.
This ruby gem converts time of day to seconds since midnight and back. The seconds value is stored in the database and can be used for calculations and validations.
Define the time of day attributes:
class BusinessHour < ActiveRecord::Base
time_of_day_attr :opening, :closing
end
Converts time of day to seconds since midnight when a string was set:
business_hour = BusinessHour.new(opening: '9:00', closing: '17:00')
business_hour.opening
=> 32400
business_hour.closing
=> 61200
To convert back to time of day:
TimeOfDayAttr.l(business_hour.opening)
=> '9:00'
TimeOfDayAttr.l(business_hour.closing)
=> '17:00'
You could also omit minutes at full hour:
TimeOfDayAttr.l(business_hour.opening, omit_minutes_at_full_hour: true)
=> '9'
I would store the starting hour and the duration within the database, using two integer columns.
By retrieving both values, you could convert the starting hour as in (assuming that you know the day already:
# assuming date is the date of the day, datetime will hold the start time
datetime = date.change({:hour => your_stored_hour_value , :min => 0 , :sec => 0 })
# calculating the end time
end_time = datetime + your_stored_duration.seconds
Otherwise, hava a look at Chronic. The gem makes handling time a little bit easier. Note that the changemethod is part of rails, and not available in plain Ruby.
The documentation on DateTime for plain Ruby can be found here.
Also, whatever you do, don't start storing your dates/time in 12-hour format, you can use I18nin Rails to convert the time:
I18n.l Time.now, :format => "%I.%m %p", :locale => :"en"
I18n.l Time.now + 12.hours, :format => "%I.%m %p", :locale => :"en"
You can also get from this notation, that you can store you duration in hours, if you want, you can then convert them rather easily by:
your_stored_value.hours
if stored as an integer, that is.
Suggestion:
Don’t worry about a specific datatype for that. A simple solution would be:
In the database, add an integer type column for start_time and another for end_time. Each will store the number of minutes since midnight.
Ex: 8:30am would be stored as 510 (8*60+30)
In the form, create a select field (dropdown) that displays all available times in time format:Ex.: 10am, 10:30am and so on.
But the actual field values that get saved in the database are their integer equivalents:
Ex: 600, 630 and so on (following the example above)
I assume you are using some kind of database for this. If you are using MySQL or Postgresql, you can use the datetime column type, which Ruby/Rails will automatically convert to/from a Time object when reading/writing to the database. I'm not sure if sqlite has something similar, but I imagine it probably does.
From the SQLite 3 website,
"SQLite does not have a storage class set aside for storing dates and/or times. Instead, the built-in Date And Time Functions of SQLite are capable of storing dates and times as TEXT, REAL, or INTEGER values:
TEXT as ISO8601 strings ("YYYY-MM-DD HH:MM:SS.SSS").
REAL as Julian day numbers, the number of days since noon in Greenwich on November 24, 4714 B.C. according to the proleptic Gregorian calendar.
INTEGER as Unix Time, the number of seconds since 1970-01-01 00:00:00 UTC.
Applications can chose to store dates and times in any of these formats and freely convert between formats using the built-in date and time functions."
You can then manipulate the values using the Date and Time functions outlined here.

Rails: find by day of week with timestamp

I need to grab the records for same day of the week for the preceeding X days of the week. There must be a better way to do it than this:
Transaction.find_by_sql "select * from transactions where EXTRACT(DOW from date) = 1 and organisation_id = 4 order by date desc limit 7"
It gets me what I need but is Postgres specific and not very "Rails-y". Date is a timestamp.
Anyone got suggestions?
How many days do you want to go back?
I have written a gem called by_star that has a dynamic finder suited for finding up to a certain number of days in the past. If the number of days was always a number you could use this finder:
Transaction.as_of_3_days_ago
If it was dynamic then I would recommend using something such as future or between, depending on if you have transactions in the future (i.e. time travel):
Transaction.future(params[:start_date].to_time)
Transaction.between(params[:start_date].to_time, Time.now)
AFAIK Rails has no any methods to do this by other way. So best, and faster, solution - build DOW index on date column and use your query.

I'm getting "Invalid month in date" trying to run this?

I'm trying to run the following db command against Informix:
delete from table1
where u_id in (select u_id
from table2
where c_id in (select c_id
from ptable
where name = 'Smith'
and dob = '29-08-1946'));
I pass this in as a string to the db.ExecuteNonQuery method in the MS Data Application block and I get the above error?
To get the date format '29-08-1946' to work, you need your DBDATE environment variable set to a value such as "DMY4-" (or "DMY4/"). These are standard variations for the UK (I used them for years; I now use "Y4MD-" exclusively, which matches both ISO 8601:2004 (Date formats) and ISO 9075 (SQL), except when debugging someone else's environment). There are other environment variables that can affect date formatting - quite a lot of them, in fact - but DBDATE takes priority over the others, so it is the big sledgehammer that fixes the problem.
One of the problems is that your notation using a plain string is not portable between US and UK (and ISO) settings of DBDATE. If you have a choice, the neutral constructor for dates is the MDY() function:
WHERE dob = MDY(8,29,1946)
This works regardless of the setting of DBDATE. You can probably use TO_DATE() too:
SELECT TO_DATE('29-08-1946', '%d-%m-%Y') FROM dual;
This generated '1946-08-29 00:00:00.00000' for me - the function generates a DATETIME YEAR TO FRACTION(5) value, but those convert reliably to DATE values in Informix.
You can also use the DATE() function or an explicit cast to DATE (either CAST('29-08-1946' AS DATE) or '29-08-1946'::DATE), but both of those are subject to the whims of the locale of the users.
Your date field is improperly formatted. Since there is no 29th month in the year 1946 that is what is causing the error.
I'd try just swapping the month and day. 08-29-1946.
The way the day and month parts of a date string are read in can depend on your computer's culture settings.
It is always safer to pass date strings to a database in the form 'dd-MMM-yyyy' (i.e. '29-aug-1946')
It's even safer to pass them as YYYY-MM-DD, the dd-MMM-yyyy in that example will fail on a server with a (for example) French locale.

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