gistfile1.txt

table_a
col_a	col_b
a		foo	
b		bar
c		baz
d		bam
e		meep
f		moop
g		pluh


table_b
col_c	col_d
g		22
e		1
j		5
n		4
q		8
a		43
y		23
f		66
x		54
e		12
u		21
n		32
g		4
f		1

How would I find all rows in table_b that do not have a match between table_a.col_a and table_b.col_c?

In other words, how do I get it to return:

table_b
col_c	col_d
e		1
j		5
n		4
q		8
y		23
x		54
u		21