使用LEAD Function并在一个SQL查询中进行演算

Question

Having Lead function and doing calculation(deduct) in ONE select statement instead of using nested select statement to achieve the results

Below shows my current not working sql statement. CurrentDate - Nxcurrentdate and having a column with showing the difference:

SELECT 
   ID, 
   CURRENTDATE,
   LEAD(CURRENTDATE,1) OVER ( PARTITION BY ID ORDER BY  ID, CURRENTDATE ) NX_DATE,
   NX_DATE - CURRENTDATE AS DATE_DIFF 
FROM TABLEA

Expected results should be:

   ID   CurrentDate   NxDate    DateDiff

Answer 1

you can use datediff(interval, date1, date2) and getdate()

Select *, DATEDIFF(day, t1.CURRENTDATE, t1.NX_DATE) AS DATE_DIFF) from (
    SELECT 
    ID, getdate() as CURRENTDATE,
    LEAD(getdate(),1) OVER ( PARTITION BY ID ORDER BY  ID, getdate()) NX_DATE
FROM TABLEA) t1

Answer 2

You can try below:

SELECT 
  ID, CURRENTDATE,
  LEAD(CURRENTDATE,1) OVER ( PARTITION BY ID ORDER BY ID, CURRENTDATE ) NX_DATE,
  datediff(day,CURRENTDATE,LEAD(CURRENTDATE,1) OVER ( PARTITION BY ID ORDER BY ID, CURRENTDATE)) AS DATE_DIFF
from tablename