Will ANSI JOIN vs. non-ANSI JOIN queries perform differently?

Question

I have my business-logic in ~7000 lines of T-SQL stored procedures, and most of them has next JOIN syntax:

SELECT A.A, B.B, C.C
FROM aaa AS A, bbb AS B, ccc          


        

Answer 1

The second construct is known as the "infixed join syntax" in the SQL community. The first construct AFAIK doesn't have widely accepted name so let's call it the 'old style' inner join syntax.

The usual arguments go like this:

Pros of the 'Traditional' syntax: the predicates are physically grouped together in the WHERE clause in whatever order which makes the query generally, and n-ary relationships particularly, easier to read and understand (the ON clauses of the infixed syntax can spread out the predicates so you have to look for the appearance of one table or column over a visual distance).

Cons of the 'Traditional' syntax: There is no parse error when omitting one of the 'join' predicates and the result is a Cartesian product (known as a CROSS JOIN in the infixed syntax) and such an error can be tricky to detect and debug. Also, 'join' predicates and 'filtering' predicates are physically grouped together in the WHERE clause, which can cause them to be confused for one another.