There is no command that you can run to delete a particular publishing job or all jobs in Publishing Service.
To do that in SQL you can run the following script:
declare @JobId uniqueidentifier
declare @ManifestId uniqueidentifier
set @JobId = 'E6CF71FC-F6FA-4A38-A2FD-80B8B9426810'
SELECT @ManifestId = [ManifestId]
FROM [dbo].[Publishing_JobManifest]
WHERE JobId = @JobId
DELETE FROM [dbo].[Publishing_ManifestStep]
WHERE ManifestId = @ManifestId
DELETE FROM [dbo].[Publishing_ManifestOperationResult]
WHERE ManifestId = @ManifestId
DELETE FROM [dbo].[Publishing_ManifestStatus]
WHERE ManifestId = @ManifestId
DELETE FROM [dbo].[Publishing_JobManifest]
WHERE JobId = @JobId
DELETE FROM [dbo].[Publishing_JobMetadata]
WHERE JobId = @JobId
DELETE FROM [dbo].[Publishing_JobQueue]
WHERE JobId = @JobId