<s>
Within	O
computing	O
,	O
author	O
O'Connell	O
defines	O
join	B-Algorithm
selection	I-Algorithm
factor	I-Algorithm
as	O
"[t]he	O
percentage	O
(	O
or	O
fraction	O
)	O
of	O
records	O
in	O
one	O
file	O
that	O
will	O
be	O
joined	B-Language
with	O
records	O
of	O
another	O
file	O
"	O
.	O
</s>
<s>
This	O
can	O
be	O
calculated	O
when	O
two	O
database	B-Application
tables	I-Application
are	O
to	O
be	O
joined	B-Language
.	O
</s>
<s>
It	O
is	O
primarily	O
concerned	O
with	O
query	B-Language
optimization	I-Language
.	O
</s>
