Избегать колонок с возможностью NULL

Nullable column (e.g. Nullable(String)) creates a separate column of UInt8 type. This additional column has to be processed every time a user works with a nullable column. This leads to additional storage space used and almost always negatively affects performance.

To avoid Nullable columns, consider setting a default value for that column. For example, instead of:

use

примечание

Consider your use case, a default value may be inappropriate.