在 sql 中将 varchar 列转换为日期

Question

I am using MSSQL server. I have a column named logDate which is of varchar type.

I have to perform operation like ' I have to delete the records which are older than 10 days '.

Which query i can use to perform this operation?

How to convert the varchar to Date type?

Here logDate varchar is in the format ddmmyyyy

I searched i got few links but i am not able to perform this operation.

Thanks for your time:)

Answer 1

You would use delete . The trick is converting logdate to a real date:

delete t
    where datefromparts(right(logdate, 4), substring(logdate, 3, 2), left(logdate, 2)) < dateadd(day, -10, convert(date, getdate()));

This deconstructs the MMDDYYYY format into the year, the month, and the date and then constructs a date from those components.

Note: This assumes that you don't actually care about the specific time.

Another way to convert the times uses string conversions:

where convert(date, right(logdate, 4) + left(logdate, 4)) < dateadd(day, -10, convert(date, getdate())

This restructures the string as YYYYMMDD, which is a standard format that is readily converted from a string to a date.

Answer 2

if you want to simply convert this to date:

declare @date nvarchar(max) = '12032020'

select cast(substring(@date, 5, 4)+substring(@date, 3, 2)+substring(@date, 1, 2) AS date)