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SQL Server internals information including my content from SQLBlog.com and SQLPerformance.com.

Sunday, 26 July 2020

A bug with Halloween Protection and the OUTPUT Clause

A bug with Halloween Protection and the OUTPUT Clause

Background

The OUTPUT clause can be used to return results from an INSERT, UPDATE, DELETE, or MERGE statement. The data can be returned to the client, inserted to a table, or both.

There are two ways to add OUTPUT data to a table:

  1. Using OUTPUT INTO
  2. With an outer INSERT statement.

For example:

-- Test table
DECLARE @Target table
(
    id integer IDENTITY (1, 1) NOT NULL, 
    c1 integer NULL
);

-- Holds rows from the OUTPUT clause
DECLARE @Output table 
(
    id integer NOT NULL, 
    c1 integer NULL
);

Sunday, 5 July 2020

How MAXDOP Really Works

How MAXDOP Really Works

A few days ago I ran a Twitter poll:

Twitter poll

The most popular answer gets highlighted by Twitter at the end of the poll, but as with many things on social media, that doesn’t mean it is correct: