How do I iterate a table according to fixed time intervals in Postgres?

问题

I want to obtain all rows for which, every interval of 48h in a given period of time, are satisfied the following conditions. Every time all of them are true, I put a flag with value 1 for it.

This is what I did so far.

DO
$$
DECLARE
  i record;
  CHARTTIME TIMESTAMP;
BEGIN
  FOR i IN SELECT * FROM schema.lab L 
            JOIN schema.icu I ON L.ID = I.ID
            WHERE L.ITEM = 50912 AND 
            L.CHARTTIME < I.INTIME AND L.CHARTTIME > (I.INTIME - INTERVAL '7 DAY')  
  LOOP
    CHARTTIME := L.CHARTTIME;
    FOREACH CHARTTIME IN ARRAY CHARTTIME + INTERVAL '48 HOUR' 
    LOOP
         IF L.VALUENUM > L.VALUENUM + 0.3 THEN 
            '1'::INTEGER AS FLAG
        END IF;
    END LOOP;
  END LOOP;
END;
$$
;

I get a syntax error. I do not know if this approach is correct, though.

ERROR:  syntax error at or near "'1'"
LINE 16:     '1'::INTEGER AS FLAG
             ^
SQL state: 42601
Character: 442

Here's the code for implementing the tables.

CREATE TABLE SCHEMA.LAB (
ID_SUB INTEGER PRIMARY KEY,
ICU INTEGER NOT NULL,
ITEM INTEGER NOT NULL,
CHARTTIME TIMESTAMP NOT NULL,
VALUENUM DOUBLE PRECISION NOT NULL);

CREATE TABLE SCHEMA.ICU (
ID INTEGER PRIMARY KEY,
INTIME TIMESTAMP NOT NULL,
ID_SUB INTEGER);

Rows of LAB are:

(1,1,50912,2020-07-17 20:48:00,0.7)
(2,2,50829,2020-07-17 20:48:00,1)
(3,3,50912,2020-07-18 20:03:00,1) 
(4,4,50912,2020-07-20 17:17:00,3.1) 
(1,1,73271,2020-05-17 17:58:00,0.2) 
(2,2,50912,2020-07-17 21:41:00,1.7)

Rows of ICU are:

(1,2020-06-17 20:01:00,1)
(2,2020-07-15 00:48:00,2) 
(3,2020-07-20 20:01:00,3) 
(4,2020-07-21 20:03:00,4)

In order to print what I want, I have to satisfy these conditions: SCHEMA.LAB L JOIN SCHEMA.ICU I ON LAB.ICU=I.ID and that L.ITEM = 50912 AND L.CHARTTIME < I.INTIME AND L.CHARTTIME > (I.INTIME - INTERVAL '7 DAY'). I am searching for an increase of the valuenum of 0.3 within every interval of 48 hours, starting from 7 days before ICU.INTIME value. So I put a flag = 1 if and only if the next valuenum has an increase of 0.3 within 48h wrt the previous one. Then I go on checking the next valuenum for the next 48 hours interval, until the LAB.charttime < ICU.intime

What I want to print is the following:

LAB.ID_SUB, ICU.ID, LAB.ITEM, LAB.CHARTTIME,        LAB.VALUENUM, ICU.INTIME           FLAG         
   3,        3,     50912,    2020-07-18 20:03:00,  1,            2020-07-20 20:01:00  1
   4,        4,     50912,    2020-07-20 17:17:00,  3.1,          2020-07-21 20:03:00. 1

回答1:

This is a stab at an answer. It really needs more complete data to be taken seriously. Here goes:

SELECT
    *, 1 AS flag
FROM
(SELECT
    *,
    valuenum - LAG(valuenum, 1) OVER(partition by item) AS diff,
    intime - LAG(intime, 1) OVER(partition by item) AS time_diff
FROM
    lab L
JOIN
    icu I
ON
    L.id_sub = I.id
WHERE
    L.item = 50912
AND
    L.charttime < I.intime AND L.charttime > (I.intime - INTERVAL '7 DAY')
) AS select_diff

WHERE
    select_diff.diff > 0.3
AND
    select_diff.time_diff <interval '48 hours';

来源：https://stackoverflow.com/questions/64857296/how-do-i-iterate-a-table-according-to-time-intervals-in-postgres

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postgresql

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