SQL query to get the output

I have two tables Table A and Table B as listed below.

Table A 
--------
X
Y

Table 
--------
X
Y

What is the SQL query to get the below output?

XX
XY
YX
YY

Answer

This looks like a cross join, to generate all possible combinations of rows between the two tables. Assuming a structure like tablea(col), tableb(col):

select a.col, b.col
from tablea a 
cross join tableb b
order by a.col, b.col

If you want to concatenate the results in a singe column:

select a.col || b.col as col
from tablea a 
cross join tableb b
order by a.col, b.col