Your original code:

create table #temp (ID int, Name varchar(20))

insert into #temp

values

(10, 'Helen'),

(20, 'Joe'),

(30, 'Blake');

;with cte as

(select * from #temp)

select * from cte

union all

;with cte as -- << error is here

(select * from #temp)

select * from cte

The error message:

Msg 102, Level 15, State 1, Line 12

Incorrect syntax near ';'.

If you double click on the error message in the messages tab it takes you directly to the error.

Also, CTE's do not start with a semicolon. The semicolon is a statement terminiator not a statement begininator.