SQL查询将整数转换为日期并查找月数差异

Question

I have 2 numbers(Integers) - 20210501 & 20210101 where the first 4 digits represent Year, next 2 digits represent Months and the last 2 digits represent Day. I want to write a SQL query to convert these integers to date and then find the difference in months between the 2 dates

Answer 1

At first convert varchar to date format and get month diff

-- SQL SERVER

SELECT DATEDIFF(MONTH, CONVERT(varchar, CAST('20210101' AS DATE), 23), CONVERT(varchar, CAST('20210501' AS DATE), 23)) month_diff

Alternate way

-- SQL SERVER

SELECT DATEDIFF(MONTH, CAST(CONVERT(varchar, CAST('20210101' AS DATE), 23) AS date), CAST(CONVERT(varchar, CAST('20210501' AS DATE), 23) AS date)) month_diff

Answer 2

Your two integers are conveniently in the right format for dates. So, you can convert to a string, then to a date and use datediff() :

select datediff(month,
                convert(date, convert(varchar(255), @val1)),
                convert(date, convert(varchar(255), @val2))
               )