Is it possible that OPERATION is a view (or synonym) and not a table?

Did you run the SELECT by itself to make sure you get results from that?

SELECT c.name 
FROM sys.tables t 
JOIN sys.columns c ON t.object_id = c.object_id
WHERE t.name...

I think this is a form of Gaps and Islands (term coined by Itzik Ben-Gan?  maybe?).  It's rather traditional in G&I to use the name "grp", so I stuck with...

Yes, only 1 OUTPUT clause.  My best suggestion is to use CASE for every column.  You can generate the CASE statements from the table definition so you don't have to...

Just now noticed the Postgre sql qualification.  I answered for SQL Server; code may or may not work on Postgre.

For (1):

SELECT GUEST.GUESTID 
FROM GUEST
WHERE GUEST.GUESTNAME='John %' /*space added because don't want name 'Johnathan' or 'Johnny'*/ AND
    EXISTS(SELECT 1 FROM BOOKING WHERE BOOKING.GUESTID=GUEST.GUESTID AND...

This ends up being a very complex task.  There are a number of threads about it on this site.

Here's a doozy (from history): Claus Philipp Maria Justinian Schenk Graf von...

An alternative:

SELECT
    Field0,
    CASE WHEN Field1_with_Field4 <> '' THEN Field1_with_Field4 ELSE Field1_without_Field4 END AS Field1,
    CASE WHEN Field1_with_Field4...

USE [DB_XYZ];

GRANT EXEC TO [MyDomain\User_1]

That includes system procs, of course.  If you prefer, you can do this:

GRANT EXEC ON SCHEMA::dbo TO [MyDomain\User_1]

I might be misinterpreting what you're saying above but,...

I've started creating a separate deadlock extended event myself.

Here's an example of how to create a deadlock ext event.  Naturally your WITH options may vary.  You can then use SSMS...

Data pages make up a clustering key. No data page exists outside a clustering key. if any data in a table with a clustering key is updated then...

I might be misinterpreting what you're saying above but,...

Paul is certainly a worthwhile authority.   I will study his article later.   I did notice this quote, which was emphasized:

A clustered table will always produce full...

Paul is certainly a worthwhile authority.   I will study his article later.   I did notice this quote, which was emphasized:

A clustered table will always produce full logging and...