MS SQL Operand类型冲突：日期与bigint不兼容

Question

I'm trying to solve a question on HackerRank using the Tabibitosan method that I read about. Here is a link to the question if you want to read it: https://www.hackerrank.com/challenges/projects/problem

Here is my error: Line 1 Operand type clash: date is incompatible with bigint

Here is my code:

SELECT MIN(start_date), MAX(end_date)
FROM (
    SELECT
        start_date, end_date,
        dense_rank() OVER (ORDER BY start_date) AS rn,
        start_date - dense_rank() OVER (ORDER BY start_date) AS grouping
    FROM projects
) AS r
GROUP BY grouping
ORDER BY COUNT(*) ASC, MIN(start_date) ASC;

There may be other issues with my code but you don't need to fix those since I'm still learning and figuring things out but I can't solve this error and searching has not helped.

Table:

Task_ID, Int
Start_date, date
End_date, date

Date format: 2015-10-31

I'm not sure why the code isn't working since the goal is basically the same as the date section of where I found the Tabibitosan Method: https://community.oracle.com/docs/DOC-915680

Answer 1

The problem is start_date - dense_rank() OVER (ORDER BY start_date) . The error is telling you the problem here; but you can't subtract a bigint value from a date . You need to use DATEADD . So replace the expression above with:

DATEADD(DAY,-(dense_rank() OVER (ORDER BY start_date)),start_date)