How to extract dates from string fields in SQL? - sql

I have field that contains strings and has dates within.
e.g
Rate (20 Jan 2020 - 19 Feb 2020)
or Rate (6 Dec 2019 - 5 Jan 2020)
I need a Start Date and End Date out of the above strings in SQL.
I can get Start Date but End Date (after the -) is a problem

Its quite crude but it will get you answers:
select left('20 Jan 2020 - 19 Feb 2020',CHARINDEX('-','20 Jan 2020 - 19 Feb 2020')-1)
,right('20 Jan 2020 - 19 Feb 2020',len('20 Jan 2020 - 19 Feb 2020') -CHARINDEX('-','20 Jan 2020 - 19 Feb 2020')-1)
CHARINDEX() will give you the position of the character you desire, in this case the dash. From there you can use LEFT(), RIGHT(), and LEN() to get the pieces out of the string that you need.
This works with SQLServer

Related

big query SQL - repeatedly/recursively change a row's column in the select statement based on the values in previous row

I have table like below
customer
date
end date
1
jan 1 2021
jan 30 2021
1
jan 2 2021
jan 31 2021
1
jan 3 2021
feb 1 2021
1
jan 27 2021
feb 26 2021
1
feb 3 2021
mar 5 2021
2
jan 2 2021
jan 31 2021
2
jan 10 2021
feb 9 2021
2
feb 10 2021
mar 12 2021
Now, I wanted to update the value in the 'end date' column of a row based on the values in the previous row 'end date' and the current row 'date'.
Say if the date in current row < end date of the previous row, I wanted to update the end date of the current row = (end date of the previous row).
I Wanted to do this repeated for all the rows (grouped by customer).
I want the output as below. Just need it in the select statement instead of a updating/inserting in a table.
Note - in below as the second row(end date) is updated with the value in the first row (jan 30 2021), now the third row value (jan 3 2021) is evaluated against the updated value in the second row (which is jan 30 2021) but not with the second row value before update (jan 31 2021).
customer
date
end date
1
jan 1 2021
jan 30 2021
1
jan 2 2021
jan 30 2021 [updated because current date < previous end date]
1
jan 3 2021
jan 30 2021[updated because current date < previous end date]
1
jan 27 2021
jan 30 2021 [updated because current date < previous end date]
1
feb 3 2021
mar 5 2021
2
jan 2 2021
jan 31 2021
2
jan 10 2021
jan 31 2021[updated because current date < previous end date]
2
feb 10 2021
mar 12 2021
I think I should go this way. I use the datasource twice just to get the way its needed to perform the operation without updating or inserting into the table.
input table:
1|2021-01-01|2021-01-30
1|2021-01-02|2021-01-31
1|2021-01-03|2021-02-01
1|2021-01-27|2021-02-26
1|2021-02-03|2021-03-05
2|2021-01-02|2021-01-31
2|2021-01-10|2021-02-09
2|2021-02-10|2021-03-12
code:
with num_raw_data as (
SELECT row_number() over(partition by customer)as num, customer,date_init,date_end
FROM `project-id.data-set.table`
), analyzed_data as(
select r.num,
r.customer,
r.date_init,
r.date_end,
case when date_init<(select date_end from num_raw_data where num=r.num-1 and customer=r.customer and EXTRACT(month FROM r.date_init)=EXTRACT(month FROM date_init)) then 1 else 0 end validation
from num_raw_data r
)
select customer,
date_init,
case when validation !=0 then (select MIN(date_end) from analyzed_data where validation=0 and customer=ad.customer and date_init<ad.date_end) else date_end end as date_end
from analyzed_data ad
order by customer,num
output:
1|2021-01-01|2021-01-30
1|2021-01-02|2021-01-30
1|2021-01-03|2021-01-30
1|2021-01-27|2021-01-30
1|2021-02-03|2021-03-05
2|2021-01-02|2021-01-31
2|2021-01-10|2021-01-31
2|2021-02-10|2021-03-12
Using column validation from analyzed_data to get to know where I should be looking for changes. I'm not sure if its fast (probably not) but it works for the scenario you bring in your question.

Sort String Value for Date in SQL

I have an issue as I am trying to select Date values stored in SQL server as String value with this format "Thu, 08 Jul 2021 06:08:20 -0700" and i need to select all table with newest date in first but I do not know how to convert this String into Date and sort it. Thanks in advance.
Table
|Thu, 08 Jul 2021 06:08:20 -0700|
|Fri, 09 Jul 2021 01:08:20 -0700|
|Sun, 11 Jul 2021 07:08:20 -0700|
output (Newest Date first)
|Sun, 11 Jul 2021 07:08:20 -0700|
|Fri, 09 Jul 2021 01:08:20 -0700|
|Thu, 08 Jul 2021 06:08:20 -0700|
Your date is just missing a valid timezone offset value so needs a ":" inserted so it's -07:00, you can do this with stuff and use substring to ignore the irrelevant day name. You don't state a specific database platform, for SQL Server you can then cast to a datetimeoffset, other databases have similar but slightly varied syntax. This assumes the strings are all formatted consistently of course.
declare #d varchar(30)='Thu, 08 Jul 2021 06:08:20 -0700'
select Cast(Stuff(Substring(#d,6,26),25,0,':') as datetimeoffset(0))
Result
2021-07-08 06:08:20 -07:00

How to calculate median monthly from date of month table?

My dataset:
Date Num_orders
Mar 21 2019 69
Mar 22 2019 82
Mar 24 2019 312
Mar 25 2019 199
Mar 26 2019 2,629
Mar 27 2019 2,819
Mar 28 2019 3,123
Mar 29 2019 3,332
Mar 30 2019 1,863
Mar 31 2019 1,097
Apr 01 2019 1,578
Apr 02 2019 2,353
Apr 03 2019 2,768
Apr 04 2019 2,648
Apr 05 2019 3,192
Apr 06 2019 2,363
Apr 07 2019 1,578
Apr 08 2019 3,090
Apr 09 2019 3,814
Apr 10 2019 3,836
...
I need to calculate the monthly median number of orders from days of the same month:
The desired results:
Month Median_monthly
Mar 2019 1,863
Apr 2019 2,768
May 2019 2,876
Jun 2019 ...
...
I tried to use function date_trunc to extract month from the dataset then group by 'month' but it didn't work out. Thanks for your help, I use Google Bigquery (#standard) environment!
Probably you tried to use PERCENTILE_CONT which can not be used with GROUP BY:
Try to use APPROX_QUANTILES(x, 100)[OFFSET(50)]. It should work with GROUP BY.
SELECT APPROX_QUANTILES](Num_orders, 100)\[OFFSET(50)\] AS median
FROM myTable
GROUP BY Month
Alternativele you can use PERCENTILE_CONT within subquery:
SELECT
DISTINCT Month, median
FROM (
SELECT
Month,
PERCENTILE_CONT(Num_orders, 0.5) OVER(PARTITION BY Month) AS median
FROM myTable
)
This would often be done using DISTINCT:
SELECT DISTINCT DATE_TRUNC(month, date),
PERCENTILE_CONT(Num_orders, 0.5) OVER (PARTITION BY DATE_TRUNC(month, date) AS median
FROM myTable;
Note: There are two percentile functions, PERCENTILE_CONT() and PERCENTILE_DISC(). They have different results when there is a "tie" in the middle of the data.

Showing data order from Monday-Sunday full week only and hide non-full week data

sorry if I'm shooting newbie questions here.
I want to create a weekly report, but for this weekly report, I want full data from Monday to Sunday
Condition:
Last 4 weeks only
Showing full week (Monday - Sunday)
Hide the result if it's not full week
If i use getdate -14, if I access the data on Wednesday, they will start counting last week from Wednesday 2 weeks ago instead of last Monday. Meanwhile, I want the report to show full week only.
Can anyone share how to do that in SQL?
Here I provide sample data:
Column name = DATE -- Column name: TOTAL_PERSON
- Fri, 1 Jun 2018 -- 10
- Sat, 2 Jun 2018 -- 4
- Sun, 3 Jun 2018 -- 12
- Mon, 4 Jun 2018 -- 15
- Tue, 5 Jun 2018 -- 10
- Wed, 6 Jun 2018 -- 3
- Thu, 7 Jun 2018 -- 1
- Fri, 8 Jun 2018 -- 13
- Sat, 9 Jun 2018 -- 9
- Sun, 10 Jun 2018 -- 23
- Mon, 11 Jun 2018 -- 5
- Tue, 12 Jun 2018 -- 3
- Wed, 13 Jun 2018 -- 1
- Thu, 14 Jun 2018 -- (TODAY)
In this case, if I am accessing on Thu 6 Jun 2018 I want to get TOTAL PERSON data from Mon, 4 Jun 2018 to Sun, 10 Jun 2018 only and not showing data from the rest since the week is not full.
Can anyone help me how to do that?
Thanks a lot!
I think you want:
where datediff(week, date, getdate()) <= 2
This counts the number of week boundaries between two dates, so it returns an entire week.
For MySQL, you can use such a select:
SELECT * FROM `myDB` WHERE `Date`
BETWEEN DATE_SUB(NOW()-INTERVAL DATE_FORMAT(CURRENT_DATE, '%w') DAY, INTERVAL 28 DAY)
AND NOW()- INTERVAL DATE_FORMAT(CURRENT_DATE, '%w') DAY
This uses the capability to transform the current day of this week into a number and substract this to get the last Sunday. from there, we select an intervall of 28 days.
(Only testet with 14 days and a very limited test-dataset, but should work)

Adding set lists of future dates to rows in a SQL query

So I am doing a cohort analysis for customers, where a cohort is a group of people who started using the product in the same month. I then keep track of each cohort's total use for every subsequent month up till present time.
For example, the first "cohort month" is January 2012, then I have "use months" January 12, Feb 12, March 12, ..., March 17(current month). One column is "cohort month", and another is "use month". This process repeats for every subsequent cohort month. The table looks like:
Jan 12 | Jan 12
Jan 12 | Feb 12
...
Jan 12 | Mar 17
Feb 12 | Feb 12
Feb 12 | Mar 12
...
Feb 12 | Mar 17
...
Feb 17 | Feb 17
Feb 17 | Mar 17
Mar 17 | Mar 17
The problem arises because I want to do forecasting for one year out for both existing and future cohorts.
That means for the Jan 12 cohort, I want to do prediction for April 17 to Mar 18.
I also want to do predictions for the April 17 cohort (which doesn't exist yet) from April 17 to Mar 18. And so on till predictions for the Mar 18 cohort in Mar 18.
I can handle the predictions, don't worry about that.
My issue is that I cannot figure out how to add in this list of (April 17 .. Mar 17) in the "use month" column before every cohort switches.
I also need to add in cohorts April 17 to Mar 18, and have the applicable parts of this list of (April 17 ... Mar 17) for each of these future cohorts.
So I want the table to look like:
Jan 12 | Jan 12
Jan 12 | Feb 12
...
Jan 12 | Mar 17
Jan 12 | Apr 17
..
Jan 12 | Mar 18
Feb 12 | Feb 12
Feb 12 | Mar 12
...
Feb 12 | Mar 17
Feb 12 | Apr 17
...
Feb 12 | Mar 18
...
...
Feb 17 | Feb 17
Feb 17 | Mar 17
...
Feb 17 | Mar 18
Mar 17 | Mar 17
...
Mar 17 | Mar 18
I know the first solution to come to mind is to do a create a list of all dates Jan 12 to Mar 18, cross join it to itself, and then left outer join to the current table I have (where cohort / use months range from Jan 12 to Mar 17). However, this is not scalable.
Is there a way I can just iteratively add in this list of the months of the next year?
I am using HP Vertica, could use Presto or Hive if absolutely necessary
I think you should use the query here below to create a temporary table out of nothing, and join it with the rest of your query. You can't do anything in a procedural manner in SQL, I'm afraid. You won't be able to get away without a CROSS JOIN. But here, you limit the CROSS JOIN to the generation of the first-of-month pairs that you need.
Here goes:
WITH
-- create a list of integers from 0 to 100 using the TIMESERIES clause
i(i) AS (
SELECT dt::DATE - '2000-01-01'::DATE
FROM (
SELECT '2000-01-01'::DATE + 0
UNION ALL SELECT '2000-01-01'::DATE + 100
) d(d)
TIMESERIES dt AS '1 day' OVER(ORDER BY d::TIMESTAMP)
)
,
-- limits are Jan-2012 to the first of the current month plus one year
month_limits(month_limit) AS (
SELECT '2012-01-01'::DATE
UNION ALL SELECT ADD_MONTHS(TRUNC(CURRENT_DATE,'MONTH'),12)
)
-- create the list of possible months as a CROSS JOIN of the i table
-- containing the integers and the month_limits table, using ADD_MONTHS()
-- and the smallest and greatest month of the month limits
,month_list AS (
SELECT
ADD_MONTHS(MIN(month_limit),i) AS month_first
FROM month_limits CROSS JOIN i
GROUP BY i
HAVING ADD_MONTHS(MIN(month_limit),i) <= (
SELECT MAX(month_limit) FROM month_limits
)
)
-- finally, CROSS JOIN the obtained month list with itself with the
-- filters needed.
SELECT
cohort.month_first AS cohort_month
, use.month_first AS use_month
FROM month_list AS cohort
CROSS JOIN month_list AS use
WHERE use.month_first >= cohort.month_first
ORDER BY 1,2
;