SQL to implement time series dislocation restoration case

 # Text version#T1
seq id startdate enddate num
1 1 2021-04-20 2021-05-03 200
2 1 2021-05-01 2021-05-24 100
3 1 2021-05-18 2021-05-31 69
4 1 2021-05-20 2021-07-31 34
5 1 2021-08-05 2021-08-25 45
6 1 2021-08-15 2021-09-25 65
 
 
# Output result ID STARTDATE ENDDATE NUM
1 2021-04-20 2021-04-30 200
1 2021-05-01 2021-05-02 300
1 2021-05-03 2021-05-17 100
1 2021-05-18 2021-05-19 169
1 2021-05-20 2021-05-23 203
1 2021-05-24 2021-05-30 103
1 2021-05-31 2021-07-30 34
1 2021-08-05 2021-08-14 45
1 2021-08-15 2021-08-25 110
1 2021-08-26 2021-09-25 65
 
 

SEQ ID STARTDATE ENDDATE NUM
1 1 2021-04-20 2021-05-03 200
2 1 2021-05-01 2021-05-24 100
3 1 2021-05-18 2021-05-31 69
4 1 2021-05-20 2021-07-31 34

id new_DATE nextSTARTDATE preEndDATE rn      
1 2021-05-24 2021-05-03 1
1 2021-05-03 2021-05-24 2021-05-01 2
1 2021-05-01 2021-05-03 2021-04-20 3
1 2021-04-20 2021-05-01 4

new_Date preENDDATE id
2021-05-24 2021-05-03 1

id STARTDATE ENDDATE
1 2021-04-20 2021-04-30
1 2021-05-01 2021-05-03
1 2021-05-04 2021-05-24

STARTDATE ENDDATE NUM
2021-04-20 2021-04-30 200
2021-05-01 2021-05-03 300
2021-05-04 2021-05-24 100

DROP TABLE IF EXISTS test_ShenLiang2025;
CREATE TABLE test_ShenLiang2025 (
  seq int DEFAULT NULL,
  id int DEFAULT NULL,
  STARTDATE date DEFAULT NULL,
  ENDDATE date DEFAULT NULL,
  NUM int DEFAULT NULL
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
 
INSERT INTO test_ShenLiang2025 VALUES ('1', '1', '2021-04-20', '2021-05-03', '200');
INSERT INTO test_ShenLiang2025 VALUES ('2', '1', '2021-05-01', '2021-05-24', '100');
INSERT INTO test_ShenLiang2025 VALUES ('3', '1', '2021-05-18', '2021-05-31', '69');
INSERT INTO test_ShenLiang2025 VALUES ('4', '1', '2021-05-20', '2021-07-31', '34');
INSERT INTO test_ShenLiang2025 VALUES ('5', '1', '2021-08-05', '2021-08-25', '45');
INSERT INTO test_ShenLiang2025 VALUES ('6', '1', '2021-08-15', '2021-09-25', '65');
 

WITH T0 AS(
SELECT id, 
   new_DATE,
   LEAD(NEW_DATE,1) OVER (PARTITION BY ID ORDER BY NEW_DATE ) nextSTARTDATE,
   LAG(NEW_DATE,1) OVER (PARTITION BY ID ORDER BY NEW_DATE ) preENDDATE,
   ROW_NUMBER()OVER(PARTITION BY ID ORDER BY new_DATE DESC) rn
   FROM
  (
  SELECT DISTINCT ID,STARTDATE new_DATE FROM test_ShenLiang2025    
   WHERE seq in (1,2) -- You can add comments to verify that only two records in the original table are taken.
  SELECT DISTINCT ID,ENDDATE new_DATE FROM test_ShenLiang2025
   WHERE seq in (1,2) -- You can add comments to verify that only 2 records in the original table are currently taken ORDER BY new_DATE 
  )A
),last AS
( SELECT new_DATE,preENDDATE,id
FROM T0 
WHERE nextSTARTDATE IS NULL
),normal AS
(
 SELECT * FROM
 (
 SELECT id, 
    ENDDATE,
    LEAD(STARTDATE,1) OVER (PARTITION BY ID ORDER BY ENDDATE ) nextSTARTDATE,
    LAG(ENDDATE,1) OVER (PARTITION BY ID ORDER BY ENDDATE ) preENDDATE
    FROM test_ShenLiang2025
 )A
 WHERE ENDDATE > preENDDATE AND ENDDATE < nextSTARTDATE
),T_Serial AS (
 
SELECT ID,ADDDATE(preENDDATE, INTERVAL 1 DAY ) STARTDATE,
new_DATE ENDDATE
FROM last 
 
UNION
 
SELECT bottom_2.ID,bottom_2.new_DATE STARTDATE,
CASE WHEN rn =3 THEN bottom_2.nextSTARTDATE 
 ELSE ADDDATE(bottom_2.nextSTARTDATE, INTERVAL -1 DAY ) END ENDDATE
FROM last 
JOIN T0 bottom_2
ON bottom_2.nextSTARTDATE<=last.preENDDATE AND bottom_2.id = last.id
),T2 AS(
SELECT B.ID,B.STARTDATE,B.ENDDATE FROM
  (
   SELECT A.*,ROW_NUMBER()OVER(PARTITION BY ID,STARTDATE ORDER BY ENDDATE) rn
   FROM
   (
   SELECT A.ID,A.STARTDATE,A.ENDDATE
   FROM T_Serial A
   LEFT JOIN normal B
   ON A.STARTDATE = B.ENDDATE AND A.ID = B.ID
   WHERE B.ENDDATE IS NULL
 
   UNION 
    
   SELECT A.ID,A.STARTDATE,B.ENDDATE   
   FROM T_Serial A
   INNER JOIN normal B
   ON ADDDATE(A.ENDDATE, INTERVAL 1 DAY ) = B.ENDDATE AND A.ID = B.ID    
   )A
  )B WHERE rn =1
)

SELECT T2.STARTDATE,T2.ENDDATE,SUM(T1.NUM) TOTAL FROM T2
JOIN test_ShenLiang2025 T1
ON T2.STARTDATE>=T1.STARTDATE 
 AND T2.ENDDATE<=T1.ENDDATE
GROUP BY T2.STARTDATE,T2.ENDDATE
ORDER BY T2.STARTDATE