Hi @Alex Chan ,

Welcome to Microsoft Q&A!
GDR (General Distribution Release) and CU (Cumulative Update) correspond to the two different service options available for the SQL Server baseline version. The baseline can be either the RTM version or the Service Pack version.
GDR Update - Cumulative contains only security updates that apply to a given baseline.
CU Update - Cumulative contains all feature fixes and security updates for a given baseline.
For any given baseline, either GDR or CU updates are optional.
If the SQL Server installation has a baseline version, then either GDR or CU updates can be selected.
If the SQL Server installation intentionally installs only past GDR updates, select Install GDR Update Pack.
If the SQL Server installation intentionally installed only previous CU updates, choose to install the CU security update package.
Note : You only have one opportunity to change a GDR update to a CU update. Once a SQL Server CU update has been applied to a SQL Server installation, there is no way to return to the GDR update path.

Subsequent releases of the CU will include previous updates. That is to say CU16 contains CU4 fixes.
Given that you have selected GDR and patched from this articlewe recommend that you install an up-to-date CU ( KB 5014353 ).
Finally, you can run "select @@version" to check your version.

For more information, please see:
https://learn.microsoft.com/en-us/sql/database-engine/install-windows/latest-updates-for-microsoft-sql-server?view=sql-server-ver15
https://support.microsoft.com/en-us/topic/kb4518398-sql-server-2019-build-versions-782ed548-1cd8-b5c3-a566-8b4f9e20293a

Best regards,
Seeya

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