Problem with and if() logic

[nikos]

		if name and month != '0' and year != '0':
			cur.execute( '''SELECT * FROM jobs WHERE clientID = (SELECT id FROM clients WHERE name = %s) and MONTH(lastvisit) = %s and YEAR(lastvisit) = %s ORDER BY lastvisit DESC''', (name, month, year) )

		elif name and year != '0':
			cur.execute( '''SELECT * FROM jobs WHERE clientID = (SELECT id FROM clients WHERE name = %s) and YEAR(lastvisit) = %s ORDER BY lastvisit DESC''', (name, year) )

		elif month != '0' and year != '0':
			cur.execute( '''SELECT * FROM jobs WHERE MONTH(lastvisit) = %s and YEAR(lastvisit) = %s ORDER BY lastvisit DESC''', (month, year) )

		elif year:
			cur.execute( '''SELECT * FROM jobs WHERE YEAR(lastvisit) = %s ORDER BY lastvisit ASC''', year )

Actually when they contained '0', which is a string which is soemthing and its different from 0 which is like sayif if month is not None.