I want to detect how many records are covered by a certain period in a RedShift table. So I queried records for various periods of time. However I've noticed a strange behavior.
When I'm trying to count a number of records for say 100 days it returns 0 no matter how many days I'm executing the query for.
SELECT count(*)
FROM main.transaction_data
WHERE tr_date > current_date - interval '100' day;
But when I query the count for several months it returns a valid count.
SELECT count(*)
FROM main.transaction_data
WHERE tr_date > current_date - interval '3 months';
Is the query for a period of 100 days incorrect?
Related
I am currently having difficulty formulating this into an sql query:
I would like to average the data of a column here twa for a duration of 10 minutes starting from the last value of the table i.e. data included here:
last date-10minutes<=date<=last date
I tried to start a first query but it does not show the right answer:
SELECT AVG(twa), horaire FROM OF50 WHERE ((SELECT horaire FROM of50 ORDER BY horaire DESC LIMIT 1)-INTERVAL '1 minutes'>horaire) ORDER BY horaire;
Regards,
Maybe this will do.
with t as (select max(horaire) maxhoraire from of50)
select AVG(of50.twa)
from of50, t
where of50.horaire between t.maxhoraire - interval '1 minute' and t.maxhoraire;
or even this may do, given that the last value can not be 'younger' then now and at least one event happened during the last minute, though it is not exactly the same and says 'the average over the last 1 minute'
select AVG(twa)
from of50
where horaire >= now() - interval '1 minute';
I want to write a SQL query in Oracle database for:
A priceindex(field name) have around 120(say) records each day and I have to display the priceindex name and today's date, if the avg of last 7 days record count is greater than Todays record count for the priceindex(group by priceindex).
Basically, There will be 56 priceindex and each should have around 120 records each day and is dump to database each day from external site. So want to make sure all records are downloaded to the database everyday.
Except for the clarification I requested in a Comment to your question (having to do with "how can we know today's final count, when today is not over yet), the problem can be solved along the following lines. Not tested since you didn't provide sample data.
From your table, select only the rows where the relevant DATE is between "today" - 7 and "today" (so there are really EIGHT days: the seven days preceding today, and today). Then group by PRICEINDEX. Count total rows for each group, and count rows just for "today". The rows for "today" should be less than 1/8 times the total count (this is easy algebra: this is equivalent to being less than 1/7 times the count of OTHER days).
Such conditions, at the group level, must be in the HAVING clause.
select priceindex
from your_table
where datefield >= trunc(sysdate) - 7 and datefield < trunc(sysdate) + 1
group by priceindex
having count(case when datefield >= trunc(sysdate) then 1 end) < 1/8 * count(*)
;
EDIT The OP clarified that the query runs every day at midnight; this means that "today" should actually mean "yesterday" (the day that just ended). In Oracle, and probably in all of computing, midnight belongs to the day that BEGINS at midnight, not the one that ends at midnight. The time-of-day at midnight is 00:00:00 (beginning of the new day), not 24:00:00.
So, the query above will have to be changed slightly:
select priceindex
from your_table
where datefield >= trunc(sysdate) - 8 and datefield < trunc(sysdate)
group by priceindex
having count(case when datefield >= trunc(sysdate) - 1 then 1 end)
< 1/8 * count(*)
;
I am using Postgres v9.2.6.
Have a system with lots of devices that take measurements. These measurements are stored in
table with three fields.
device_id
measurement (Indexed)
time (Indexed)
There could be 10 Million measurements in a single year. Most of the time the user is only interested in 100 min max pairs within equal interval for a certain period, for example in last 24 hours or in last 53 weeks. To get these 100 mins and maxs the period is divided into 100 equal intervals. From each interval min and max is extracted. Would you recommend the most efficient approach to query the data? So far I have tried the following query:
WITH periods AS (
SELECT time.start AS st, time.start + (interval '1 year' / 100) AS en FROM generate_series(now() - interval '1 year', now(), interval '1 year' / 100) AS time(start)
)
SELECT * FROM sample_data
JOIN periods
ON created_at BETWEEN periods.st AND periods.en AND
customer_id = 23
WHERE
sample_data.id = (SELECT id FROM sample_data WHERE created_at BETWEEN periods.st AND periods.en ORDER BY sample ASC LIMIT 1)
This test approach took over a minute for 1 million points on MacBook Pro.
Thanks...
Sorry about that. It was actually my question and looks like the author of this post caught cold so I ca not ask him to edit it. I've posted "more good" question here - Slow PostgreSQL Query for Mins and Maxs within equal intervals in a time period. Could you please close this question?
I have a PostgreSQL database in which one table rapidly grows very large (several million rows every month or so) so I'd like to periodically archive the contents of that table into a separate table.
I'm intending to use a cron job to execute a .sql file nightly to archive all rows that are older than one month into the other table.
I have the query working fine, but I need to know how to dynamically create a timestamp of one month prior.
The time column is stored in the format 2013-10-27 06:53:12 and I need to know what to use in an SQL query to build a timestamp of exactly one month prior. For example, if today is October 27, 2013, I want the query to match all rows where time < 2013-09-27 00:00:00
Question was answered by a friend in IRC:
'now'::timestamp - '1 month'::interval
Having the timestamp return 00:00:00 wasn't terrible important, so this works for my intentions.
select date_trunc('day', NOW() - interval '1 month')
This query will return date one month ago from now and round time to 00:00:00.
When you need to query for the data of previous month, then you need to query for the respective date column having month values as (current_month-1).
SELECT *
FROM {table_name}
WHERE {column_name} >= date_trunc('month', current_date-interval '1' month)
AND {column_name} < date_trunc('month', current_date)
The first condition of where clause will search the date greater than the first day (00:00:00 Day 1 of Previous Month)of previous month and second clause will search for the date less than the first day of current month(00:00:00 Day 1 of Current Month).
This will includes all the results where date lying in previous month.
I'm trying to develop an 'upcoming listings' puller for my website, however the following query does not seem to be performing as it should.
The SQL:
SELECT * FROM listings WHERE start_date > DATE_SUB( CURDATE(), INTERVAL 3 MONTH )
Rather than pulling listings from 3 months ahead it pulls all listings?
If you want to work with 'future' records, you should use DATE_ADD instead:
SELECT *
FROM listings
WHERE start_date
BETWEEN CURDATE()
AND DATE_ADD(CURDATE(), INTERVAL 3 MONTH);
Note that BETWEEN ... AND clause is inclusive: in other words, you'll have records for start_date equal both to the current's one and the one exactly 3 months after. If that's not the desired outcome, just use separate two conditions:
WHERE start_date > CURDATE()
AND start_date < DATE_ADD(CURDATE(), INTERVAL 3 MONTH);
As it stands now, you collect all the records having start_date set to later than 3 months before the current date. That probably includes the whole dataset.