How many customers belong to the household segment in Germany?
household segment refers to c_mktsegment = 'household'; Germany refers to n_name = 'Germany'
SELECT COUNT(T1.c_name) FROM customer AS T1 INNER JOIN nation AS T2 ON T1.c_nationkey = T2.n_nationkey WHERE T1.c_mktsegment = 'HOUSEHOLD' AND T2.n_name = 'GERMANY'