Two Aliase one table - explain
Hi all
Please explain(internal process of) the below code.
Code:
SELECT
b.measure_unit_type_name defaultType,
c.measure_unit_type_name actualType,
(a.default_serving_amt * b.measure_unit_amt) defaultFactor,
(12 * c.measure_unit_amt) actualFactor
FROM
FOOD a,
MEASURE_UNIT b,
MEASURE_UNIT c
WHERE a.default_measure_unit_nr = b.measure_unit_nr
AND a.food_nr = 113
AND c.measure_unit_nr = 12
here in measure_unit table two aliase name is given,if i remove one that is 'c' and if i query with 'b' alone it returns null value. one of my friend said it is cross joining but coundn't get the clear picture,if any document is available please give me the link.(google doesn't helps a lot)
Thanks in advance.,