Now watch A, field f1 content:
Item1
Item2
Item3

Table B, field f1 content:
A
B

Requirements for view the results are as follows:

Item1 A
Item2 A
Item3 A
Item1 B
Item2 B
Item3 B

When table B content change to:
A
B
C
, check the results to:

Item1 A
Item2 A
Item3 A
Item1 B
Item2 B
Item3 B
Item1 C
Item2 C
Item3 C

Now made cross connection way is query
1, select A.f A.f 1 from A, B


Is there no higher performance deal? A table of data is larger than 5 million