What the hell are you talking about?

You can only select, you can't nest cte, the query planner has no understanding of joins that cross cte boundaries so they are totally unoptimized, you can't use distinct or group by or etcetc. Really the CTE implementation in SqlServer is basically a parser level hack.

> You can only select

   with x as (...)
   update x set ...

> you can't nest cte

ok but you can linearise them

   with x as (...), y as (...)

> the query planner has no understanding of joins that cross cte boundaries so they are totally unoptimized

utter, reeking garbage.

> you can't use distinct or group

more garbage. I have. Show me an example of it not working.

(Edited for less rudeness)

so you can do this?

  WITH t AS (
      DELETE FROM foo 
  )
  DELETE FROM bar;

Or can you only use SELECT for WITH queries? Did you not realize that other databases and the SQL standard allow you to do this?

Yes on the final query of the CTE you can do all sorts of things, but that's way less useful if you can't do them in all the component queries.

Show me any sql dialect that will allow that CTE you give here (edit; and what on earth is that supposed to actually mean)

> Or can you only use SELECT for WITH queries

you can only use a select inside a cte (or should be able to) because the 'e' stands for 'expression'. It seems postgres does allow an insert with and output which sort of makes sense but I doubt it's in the standard.

Your last sentence makes no sense to me. Give an example.

Also you failed to give an example that group by/distiinct weren't allowed in ctes.