How to join two result sets from same table with different conditions on same column?
If you want number and kilograms to appear as a single column (comma separated), do this:

SELECT GROUP_CONCAT(uom_name) UnitsOfMeasure
FROM unit_of_measure WHERE uom_id IN (1,2);


If you want number and kilograms to appear as a single column (space separated), do this:

SELECT GROUP_CONCAT(uom_name SEPARATOR ' ') UnitsOfMeasure
FROM unit_of_measure WHERE uom_id IN (1,2);


If you want number and kilograms to appear as separate columns, do this:

SELECT * FROM
(SELECT uom_name AS uomname1 FROM unit_of_measure WHERE uom_id=1) A,
(SELECT uom_name AS uomname2 FROM unit_of_measure WHERE uom_id=2) B;


Give it a Try !!!