Alan.B (9/2/2014)
In this query this is what happens:1. A is joined to B to create AB.
2. AB is joined to C to create ABC
Let's say you had 5 tables involved in this order A, B, C, D & E
1. A is joined to B to create AB.
2. AB is joined to C to create ABC
...
5. ABCD is joined to E to create ABCDE
Except that the join order is not guaranteed.
It could happen the following:
1. B is joined to C to create BC.
2. D is joined to E to create DE.
3. BC is joined to DE to create BCDE.
4. A is joined to BCDE to create ABCDE.
Or any other combination that the engine will define as the best (technically not always the best but that's a larger subject and won't get into details).
I'm sure Itzek Ben Gan's books will explain better this situations.