So I want to make a query to show me if a certain calendar week has all 7 Day.
It would be okay if it just returns the numbers 1-7.
The table that I have contains articles of the 3 month of 2020 but even so the first week just contains Wednesday to Sunday it still counts it as a calendar week.
With that select I would make pl/sql Script to check it and if yes something happens.
This is an example of the Table:
Date Articel_Id
14.10.2020 78
15.10.2020 80
16.10.2020 96
17.10.2020 100
18.10.2020 99
Can I Use to_char() to check if Calendar Week has all 7 Days ?
If yes, how ?
The challenging is actually defining the weeks. If you want to define them using the ISO standard, then aggregate:
select to_char(date, 'IYYYY-IW') as yyyyww,
count(distinct trunc(date)) as num_days
from t
group by to_char(date, 'IYYYY-IW')
order by yyyyww;
This counts the number of days per week. I'm not sure if you want to filter, have a flag, or what the result set should look like. For filtering, using a having clause, such as having count(distinct trunc(date)) = 7.
Related
I have approximately the same table (excluding count column). I want to calculate the number of working days (Mon-Fri) and exclude public holidays.
I tried to try the following query
SELECT count(distinct(date)) from MYDB where dummy <> 1
However, it gives the only total number of days including weekends. Additionally, if use this command it counts distinct dates, however, my dates do not show a full month, so another logic should've used. Could you help to figure out which code is better to use?
there should be a function in Vertica that extracts weekday from date, so to exclude weekends you'll need to add another condition like
extract(dow from date) not in (6,0)
(6 is Sat, 0 is Sun in this case)
I am working with an existing E-commerce database. Actually, this process is usually done in Excel, but we want to try it directly with a query in PostgreSQL (version 10.6).
We define as an active customer a person who has bought at least once within 1 year. This means, if I analyze week 22 in 2020, an active customer will be the one that has bought at least once since week 22, 2019.
I want the output for each week of the year (2020). Basically what I need is ...
select
email,
orderdate,
id
from
orders_table
where
paid = true;
|---------------------|-------------------|-----------------|
| email | orderdate | id |
|---------------------|-------------------|-----------------|
| email1#email.com |2020-06-02 05:04:32| Order-2736 |
|---------------------|-------------------|-----------------|
I can't create new tables. And I would like to see the output like this:
Year| Week | Active customers
2020| 25 | 6978
2020| 24 | 3948
depending on whether there is a year and week column you can use a OVER (PARTITION BY ...) with extract:
SELECT
extract(year from orderdate),
extract(week from orderdate),
sum(1) as customer_count_in_week,
OVER (PARTITION BY extract(YEAR FROM TIMESTAMP orderdate),
extract(WEEK FROM TIMESTAMP orderdate))
FROM ordertable
WHERE paid=true;
Which should bucket all orders by year and week, thus showing the total count per week in a year where paid is true.
references:
https://www.postgresql.org/docs/9.1/tutorial-window.html
https://www.postgresql.org/docs/8.1/functions-datetime.html
if I analyze week 22 in 2020, an active customer will be the one that has bought at least once since week 22, 2019.
Problems on your side
This method has some corner case ambiguities / issues:
Do you include or exclude "week 22 in 2020"? (I exclude it below to stay closer to "a year".)
A year can have 52 or 53 full weeks. Depending on the current date, the calculation is based on 52 or 53 weeks, causing a possible bias of almost 2 %!
If you start the time range on "the same date last year", then the margin of error is only 1 / 365 or ~ 0.3 %, due to leap years.
A fixed "period of 365 days" (or 366) would eliminate the bias altogether.
Problems on the SQL side
Unfortunately, window functions do not currently allow the DISTINCT key word (for good reasons). So something of the form:
SELECT count(DISTINCT email) OVER (ORDER BY year, week
GROUPS BETWEEN 52 PRECEDING AND 1 PRECEDING)
FROM ...
.. triggers:
ERROR: DISTINCT is not implemented for window functions
The GROUPS keyword has only been added in Postgres 10 and would otherwise be just what we need.
What's more, your odd frame definition wouldn't even work exactly, since the number of weeks to consider is not always 52, as discussed above.
So we have to roll our own.
Solution
The following simply generates all weeks of interest, and computes the distinct count of customers for each. Simple, except that date math is never entirely simple. But, depending on details of your setup, there may be faster solutions. (I had several other ideas.)
The time range for which to report may change. Here is an auxiliary function to generate weeks of a given year:
CREATE OR REPLACE FUNCTION f_weeks_of_year(_year int)
RETURNS TABLE(year int, week int, week_start timestamp)
LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
ROWS 52 COST 10 AS
$func$
SELECT _year, d.week::int, d.week_start
FROM generate_series(date_trunc('week', make_date(_year, 01, 04)::timestamp) -- first day of first week
, LEAST(date_trunc('week', localtimestamp), make_date(_year, 12, 28)::timestamp) -- latest possible start of week
, interval '1 week') WITH ORDINALITY d(week_start, week)
$func$;
Call:
SELECT * FROM f_weeks_of_year(2020);
It returns 1 row per week, but stops at the current week for the current year. (Empty set for future years.)
The calculation is based on these facts:
The first ISO week of the year always contains January 04.
The last ISO week cannot start after December 28.
Actual week numbers are computed on the fly using WITH ORDINALITY. See:
PostgreSQL unnest() with element number
Aside, I stick to timestamp and avoid timestamptz for this purpose. See:
Generating time series between two dates in PostgreSQL
The function also returns the timestamp of the start of the week (week_start), which we don't need for the problem at hand. But I left it in to make the function more useful in general.
Makes the main query simpler:
WITH weekly_customer AS (
SELECT DISTINCT
EXTRACT(YEAR FROM orderdate)::int AS year
, EXTRACT(WEEK FROM orderdate)::int AS week
, email
FROM orders_table
WHERE paid
AND orderdate >= date_trunc('week', timestamp '2019-01-04') -- max range for 2020!
ORDER BY 1, 2, 3 -- optional, might improve performance
)
SELECT d.year, d.week
, (SELECT count(DISTINCT email)
FROM weekly_customer w
WHERE (w.year, w.week) >= (d.year - 1, d.week) -- row values, see below
AND (w.year, w.week) < (d.year , d.week) -- exclude current week
) AS active_customers
FROM f_weeks_of_year(2020) d; -- (year int, week int, week_start timestamp)
db<>fiddle here
The CTE weekly_customer folds to unique customers per calendar week once, as duplicate entries are just noise for our calculation. It's used many times in the main query. The cut-off condition is based on Jan 04 once more. Adjust to your actual reporting period.
The actual count is done with a lowly correlated subquery. Could be a LEFT JOIN LATERAL ... ON true instead. See:
What is the difference between LATERAL and a subquery in PostgreSQL?
Using row value comparison to make the range definition simple. See:
SQL syntax term for 'WHERE (col1, col2) < (val1, val2)'
I'm currently running the following sql statement in JasperReports Server to bring back my data using derived tables.
Select count(createddate) as ModulesCreatedDuringPastWeek,
count(updateddate) as ModulesUpdatedDuringPastWeek,
createddate,
updateddate
from merchendisingmodule
group by merchendisingmodule.createddate, merchendisingmodule.updateddate
However when grouping my data, I am only able to do it in Year, quarter, month and day. However for my report I'm needing the data to be group weeks, and so I was wondering what I will need to add to my code to do this.
DATEADD(D,-DATEPART(weekday,createddate)+1,createddate)
I use this method to prevent issues around the year transitions (week 53 in first days of januari and also in the last days of december, will group days together that are 360 days apart).
I use the first day of the week, instead of week numbers. I can use these dates to group by.
Also this will ensure that every week is 7 days long, instead of the last week of the year being only 3 or 4 days long.
Btw, in this example the first day of the week is sunday.
If your dates include time, use:
CAST(FLOOR(CAST(createddate AS FLOAT)) AS DATETIME)
instead of createddate in the above SYNTAX
Table:
DayOfWeek Enrollments
Monday 35
Monday 12
Saturday 25
Tuesday 15
Monday 9
Tuesday 15
Basically I'm trying to sum the total enrolments for each day.
so the Output will look like:
DayOfWeek Enrollments
Monday 56
Saturday 25
Tuesday 30
I've spent around 4 hours trying to work this out trying many many different ways but no luck.
The problem I'm having is i can count how many enrollments for each day but can't have it aligned with the correct day when i run the query e.g. I want The total to be on the same line as the day it was calculated from. (I hope that is clear enough)
Group by DayOfWeek, and ask for the sum of Enrollments within each group. The SQL will look like this.
SELECT DayOfWeek, Sum(Enrollments) AS SumOfEnrollments
FROM YourTable
GROUP BY DayOfWeek;
If you're using the Access query designer to create this, select your fields, then click the symbol for "Totals" query (Greek character sigma). In the "Total:" row of the design grid, select Group By and Sum for the appropriate fields.
Greetings SQL gurus,
I don't know if you can help me, but I will try. I have several large databases grouped by year (each year in a different database). I want to be able to compare values from a particular week from one year to the next. For example, "show me week 17 of 2008 vs. week 17 of 2002."
I have the following definition of weeks that ideally I would use:
Only 52 weeks each year and 7 days a week (that only takes 364 days),
The first day of the first week starts from January 2nd - which means we do not use January 1st data, and
In leap year, the first day of the first week ALSO starts from the January 2nd plus we skip Feb. 29.
Any ideas?
Thanks in advance.
Best to avoid creating a table because then you have to update and maintain it to get your queries to work.
DatePart('ww',[myDate]) will give you the week number. You may run into some issues though deciding which week belongs to which year - for example if Jan 1 2003 is on Wednesday does the week belong as week 52 in 2002 or week 1 in 2003? Your accounting department will have a day of the week that is your end of week (usually Sat). I usually just pick the year that has the most days in it. DatePart will always count the first week as 1 and in the case of the example above the last week as 53. You may not care that much either way. You can create queries for each year
SELECT DatePart('ww',[myDate]) as WeekNumber,myYearTable.* as WeekNumber
FROM myYearTable
and then join the queries to get your data. You'll loose a couple days at the end of the year if one table has 52 weeks and one has 53 (most will show as 53). Or you can do it by your weekending day - this always gives you Saturday which would push a late week into the following year.
(7-Weekday([myDate]))+[myDate]
then
DatePart('ww',(7-Weekday([myDate]))+[myDate])
Hope that helps
To get the week number
'to get the week number in the year
select datepart( week, datefield)
'to get the week number in the month
select (datepart(dd,datefield) -1 ) / 7 + 1
You don't need to complicate things thinking about leap years, etc. Just compare weeks mon to sun
SInce you havea a specifc defintion of when the week starts that is differnt that the standard used by the db, I think a weeks table is the solution to your problem. For each year create a table that defines the dates contained in each week and the week number. Then by joining to that table as well as the relevant other tables, you can ask for just the data for week 17.
Table structure
Date Week
20090102 1
20090103 1
etc.
I needed to create a query that shows BOTH year AND week numbers, like 2014-52. The year shows correct when you use the Datepart() formula to convert week 53 to week 52 in the previous year, but shows the wrong year for the week that was week 1 previously that should be week 52 now. It show that week as 2015-52 instead of 2014-52.
Furthermore, it sorts the data wrong if you only use only the week number, eg:
2014-1,2014-11,2014-2
To overcome this I created the following query to insert a 0 and also to check for days in week 1 that should still fall under week 52.
ActualWeek: IIf(DatePart("ww",[SomeDate],1,3)=52 And DatePart("ww",[SomeDate])=1, DatePart("yyyy",[SomeDate],1,3)-1,DatePart("yyyy",[SomeDate],1,3)) & "-" & IIf(DatePart("ww",[SomeDate],1,3)<10,"0" & DatePart("ww",[SomeDate],1,3),DatePart("ww",[SomeDate],1,3))