MySQL-forespørgselsperioder og værdien af ​​maksimalt fald i forhold til foregående maksimumværdi

Jeg formoder, at de kan optimeres noget, men disse forespørgsler burde give dig de resultater, du ønsker. De deler de samme første 3 CTE'er, som genererer diff_max værdi for hver data_max . I den første forespørgsel leder vi lige efter en ændring i den værdi (fra NULL til en værdi eller et fald i værdien) for at generere outputrækkerne. Den anden forespørgsels 4. og 5. CTE'er ligner den første forespørgsel, men vi tilføjer en RANK til diff_max værdier, så vi kan JOIN minimumsværdien (med den tilhørende dato) til date_diff_from og date_diff_to værdier fra 6. CTE (som er det samme som mit svar på dine andet spørgsmål ).

Spørgsmål 1:

WITH cte AS (SELECT DATE(`date_time`) AS `date`,
                    `data`,
                    MAX(`data`) OVER (ORDER BY `date_time`) AS `data_max`
             FROM `test`),
cte2 AS (SELECT `date`,
                `data`,
                `data_max`,
                CASE WHEN `data` < `data_max` THEN `data` - `data_max` END AS `data_diff`
         FROM cte),
cte3 AS (SELECT `date`, 
                MIN(`data_diff`) OVER (PARTITION BY `data_max` ORDER BY `date`) AS `diff_max`
         FROM cte2),
cte4 AS (SELECT `date`, `diff_max`, LAG(`diff_max`) OVER (ORDER BY `date`) AS `old_diff_max`
         FROM cte3)
SELECT `date`, `diff_max`
FROM cte4
WHERE `diff_max` < `old_diff_max` OR `old_diff_max` IS NULL AND `diff_max` IS NOT NULL
 

Output:

date        diff_max
2017-01-04  -3
2017-01-09  -7
2017-01-11  -10
2017-01-13  -2
 

Spørgsmål 2:

WITH cte AS (SELECT DATE(`date_time`) AS `date`,
                    `data`,
                    MAX(`data`) OVER (ORDER BY `date_time`) AS `data_max`
             FROM `test`),
cte2 AS (SELECT `date`,
                `data`,
                `data_max`,
                CASE WHEN `data` < `data_max` THEN `data` - `data_max` END AS `data_diff`
         FROM cte),
cte3 AS (SELECT `data_max`, `date`, 
                MIN(`data_diff`) OVER (PARTITION BY `data_max` ORDER BY date) AS `diff_max`
         FROM cte2),
cte4 AS (SELECT `data_max`, `date`, `diff_max`, 
                LAG(`diff_max`) OVER (ORDER BY `date`) AS `old_diff_max`
         FROM cte3),
cte5 AS (SELECT `date`, `diff_max`, 
                RANK() OVER (PARTITION BY `data_max` ORDER BY `diff_max`) AS `diff_rank`
         FROM cte4
         WHERE `diff_max` < `old_diff_max` OR `old_diff_max` IS NULL AND `diff_max` IS NOT NULL),
cte6 AS (SELECT `data_max`, 
                MIN(CASE WHEN `data_diff` IS NOT NULL THEN date END) AS diff_date_from,
                MAX(CASE WHEN `data_diff` IS NOT NULL THEN date END) AS diff_date_to
         FROM cte2
         GROUP BY `data_max`
         HAVING diff_date_from IS NOT NULL)
SELECT diff_date_from, diff_date_to, `date` AS diff_max_date, `diff_max`
FROM cte6
JOIN cte5 ON cte5.date BETWEEN cte6.diff_date_from AND cte6.diff_date_to
WHERE cte5.diff_rank = 1
 

Output: