If you need to select the records between 2 dates in MS SQL, where the DateTime column contains both Date and Time, you can use SQL functions for WHERE clause and avoid of adding the time information like '23:59:59.000'. Though you can do it and this way.

Using function CAST:

where CAST(TIMESTAMP as date) between '2023-05-29' AND '2023-05-30'

Using function CONVERT:

where CONVERT(date, TIMESTAMP) between '2023-05-29' AND '2023-05-30'

The requests looks like these respectively:

SELECT Title, Timestamp, DocType from MyTable where CAST(TIMESTAMP as date) between '2023-05-29' AND '2023-05-30'

SELECT Title, Timestamp, DocType from MyTable where CONVERT(date, TIMESTAMP) between '2023-05-29' AND '2023-05-30'