LAG() और LEAD() के साथ काम

SQL Server में Time Series Analysis

Maham Faisal Khan

Senior Data Science Content Developer

LAG() विंडो फंक्शन

SELECT
    dsr.CustomerID,
    dsr.MonthStartDate,
    LAG(dsr.NumberOfVisits) OVER (PARTITION BY dsr.CustomerID ORDER BY dsr.MonthStartDate) AS Prior,
    dsr.NumberOfVisits
FROM dbo.DaySpaRollup dsr;

CustomerID	MonthStartDate	Prior	NumberOfVisits
1	2018-12-01	NULL	49
1	2019-01-01	49	117
1	2019-02-01	117	104

LEAD() विंडो फंक्शन

SELECT
    dsr.CustomerID,
    dsr.MonthStartDate,
    dsr.NumberOfVisits,
    LEAD(dsr.NumberOfVisits) OVER (PARTITION BY dsr.CustomerID ORDER BY dsr.MonthStartDate) AS Next
FROM dbo.DaySpaRollup dsr;

CustomerID	MonthStartDate	NumberOfVisits	Next
1	2018-12-01	49	117
1	2019-01-01	117	104
1	2019-02-01	104	108

पीछे की पंक्तियों की संख्या बताना

SELECT
   dsr.CustomerID,
   dsr.MonthStartDate,
   LAG(dsr.NumberOfVisits, 2) OVER (PARTITION BY dsr.CustomerID ORDER BY dsr.MonthStartDate) AS Prior2,
   LAG(dsr.NumberOfVisits, 1) OVER (PARTITION BY dsr.CustomerID ORDER BY dsr.MonthStartDate) AS Prior1,
   dsr.NumberOfVisits
FROM dbo.DaySpaRollup dsr;

CustomerID	MonthStartDate	Prior2	Prior	NumberOfVisits
1	2018-12-01	NULL	NULL	49
1	2019-01-01	NULL	49	117
1	2019-02-01	49	117	104

विंडो और फ़िल्टर

SELECT
    Date,
    LAG(Val, 1) OVER(ORDER BY DATE) AS PriorVal,
    Val
FROM t;

Date	PriorVal	Val
2019-01-01	NULL	3
2019-01-02	3	6
2019-01-03	6	4

SELECT
    Date,
    LAG(Val, 1) OVER(ORDER BY DATE) AS PriorVal,
    Val
FROM t
WHERE
    t.Date > '2019-01-02';

Date	PriorVal	Val
2019-01-03	NULL	4

विंडो, फ़िल्टर, और CTEs

WITH records AS (
  SELECT
      Date,
      LAG(Val, 1) OVER(ORDER BY Date) AS PriorVal,
      Val
  FROM t
)
SELECT
    r.Date,
    r.PriorVal,
    r.Val
FROM records r
WHERE
    r.Date > '2019-01-02';

Date	PriorVal	Val
2019-01-03	6	4

अभ्यास करते हैं!

SQL Server में Time Series Analysis