What is the best way to perform query by ID or instead get all?

I have to do a query filter but I don’t want to repeat code. I would like to do it in one simple query, the simplest possible.

Technology

SQL Server v18

The Acceptance Criteria

Get by ID if the ID has a value (one single record in this case) OR IF ID = NULL then GET ALL

I’ve been trying with AND, ORs, IS NOT NULL, etc. But I would like to get the records in a simplest query.

Currently this is my query:

DECLARE @EventLogId int = null
SET @EventLogId = NULL

-- Insert statements for procedure here
SELECT 
    EL.EventLogId,
    EL.EventLogDateTime,
    EL.Username,
    EL.EventLogTypeId,
    EL.ActionTypeId,
    EL.ProfessionalId,
    EL.BioId,
    EL.[Message],
    EL.ExceptionMessage,
    EL.StackTrace,
    ELTypes.[Name] AS EventLogTypeName,
    ATypes.[Name] AS ActionTypeName
FROM 
    dbo.EventLog EL
INNER JOIN 
    EventLogType ELTypes ON ELTypes.Id = EL.EventLogTypeId
INNER JOIN 
    ActionTypes ATypes ON ATypes.ActionTypeId = EL.ActionTypeId
WHERE 
    EL.EventLogId = @EventLogId 
    AND NOT(EL.EventLogId IS NULL)

Thanks for the help!

>Solution :

Just another option … coalesce()

WHERE  EL.EventLogId = coalesce(@EventLogId,EL.EventLogId)