What is going on with SQL Server there? I moved from MySQL to SQL Server and there's been a handful of gotchas but for the most part it's been an incredibly sim

What is going on with SQL Server there? I moved from MySQL to SQL Server and there's been a handful of gotchas but for the most part it's been an incredibly simple transition -- SQL Server is as close to MySQL as Postgres is in terms of query language, I should think, certainly closer than Redshift or Vertica are -- but the pairwise comparison doesn't bear it out. The author also talks about SQL Server distinct from MySQL or Postgres, which he kinda lumps together. It's rather baffling to me.