假设我有这样一个销售表：

store_id    industry_id    cust_id    amount    gender    age
       1            100       1000       1.00       M      20
       2            100       1000       2.05       M      20
       3            100       1000       3.15       M      20
       4            200       2000       5.00       F      30
       5            200       2000       6.00       F      30

以下是生成此表的代码：

CREATE TABLE t1(
    store_id int,
    industry_id int,
    cust_id int,
    amount float,
    gender char,
    age int
);
INSERT INTO t1 VALUES(1,100,1000,1.00, 'M',20);
INSERT INTO t1 VALUES(2,100,1000,2.05, 'M',20);
INSERT INTO t1 VALUES(3,100,1000,3.15, 'M',20);
INSERT INTO t1 VALUES(4,200,2000,5.00, 'F',30);
INSERT INTO t1 VALUES(5,200,2000,6.00, 'F',30);

假设我们想找出每个年龄/性别组合的消费总额。像这样：

gender    age    total_amount
    M      20            6.20
    F      30           11.00

以下代码不起作用（它抛出“操作数应包含1列”错误）：

SELECT
    ('M','F') as gender
    , (20,30) as age 
    , (SUM(CASE WHEN gender='M' AND age=20 THEN amount END)
    , SUM(CASE WHEN gender='F' AND age=30 THEN amount END)) as total_amount
FROM t1;

最好的办法是什么？