Count number of events before and after a particular event in SQL?

问题

I have a table containing date and events. There is event named 'A'. I want to find out how many events occurred before and after event 'A' in Sql Bigquery. for Example,

User           Date             Events
123          2018-02-13            D
123          2018-02-12            B
123          2018-02-10            C
123          2018-02-11            A
123          2018-02-01            X

The answer would be something like this.

  User       Event    Before   After
  123          A       2        2

I have tried many queries but its not working. Any Idea, how to solve this problem?

回答1:

below is for BigQuery Standard SQL

#standardSQL
WITH `project.dataset.events` AS (
  SELECT 123 user, '2018-02-13' dt, 'D' event UNION ALL
  SELECT 123, '2018-02-12', 'B' UNION ALL
  SELECT 123, '2018-02-11', 'A' UNION ALL
  SELECT 123, '2018-02-10', 'C' UNION ALL
  SELECT 123, '2018-02-01', 'X' 
)
SELECT user, event, before, after 
FROM (
  SELECT user, event, 
    COUNT(1) OVER(PARTITION BY user ORDER BY dt ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING) before,
    COUNT(1) OVER(PARTITION BY user ORDER BY dt ROWS BETWEEN 1 FOLLOWING AND UNBOUNDED FOLLOWING ) after
  FROM `project.dataset.events`
)
WHERE event = 'A'

回答2:

For each "A", you can get the number of events to the next "A" using row_number() and lead():

select t.*,
       (lead(seqnum) over (order by date) - seqnum - 1) as num_other_events
from (select t.*, row_number() over (order by date) as seqnum
      from t
     ) t
where event = 'A';

This produces the results for each "A". Given that you have three "A"s in your sample data and only want "2", I'm not sure what logic is used for that.

回答3:

If you want to count number of events as they appear in the table before the row with event A, there is no way to do this because BigQuery doesn't preserve physical order of rows in a table.

If you want to count Before and After using the date column, you can do

WITH
  events AS (
  SELECT
    DATE('2018-02-13') AS event_date,
    "D" AS event
  UNION ALL
  SELECT
    DATE('2018-02-12') AS event_date,
    "B" AS event
  UNION ALL
  SELECT
    DATE('2018-02-10') AS event_date,
    "C" AS event
  UNION ALL
  SELECT
    DATE('2018-02-11') AS event_date,
    "A" AS event
  UNION ALL
  SELECT
    DATE('2018-02-01') AS event_date,
    "X" AS event),
  event_a AS (
  SELECT
    *
  FROM
    events
  WHERE
    event = "A")
SELECT
  ANY_VALUE(event_a.event) AS Event,
  COUNTIF(events.event_date<event_a.event_date) AS Before,
  COUNTIF(events.event_date>event_a.event_date) AS After
FROM
  events,
  event_a

回答4:

Hope this answers your question

Create table #temp(T_date varchar(100),Events varchar(100))

insert into #temp values
('2018-02-13','A'),
('2018-02-12','B'),
('2018-02-10','C'),
('2018-02-11','A'),
('2018-02-01','X'),
('2018-02-06','A')

select max(rn)-min(rn)
from
(
select *,ROW_NUMBER() over(order by (select 1)) as rn from #temp
)a
where Events='A'

来源：https://stackoverflow.com/questions/48770680/count-number-of-events-before-and-after-a-particular-event-in-sql

标签

sql

google-bigquery

legacy-sql