ROLLUP运算符

这里为所有的顾客计算了总销售额
SELECT
client_id,
SUM(invoice_total) AS total_sales
FROM invoices
GROUP BY client_id

这里为所有的顾客计算了总销售额
添加了ROLLUP运算符语句，汇总整个结果集。
SELECT
client_id,
SUM(invoice_total) AS total_sales
FROM invoices
GROUP BY client_id WITH ROLLUP

如果想做分组统计的话
SELECT
state,
city,
SUM(invoice_total) AS total_sales
FROM invoices i
JOIN clients c USING (client_id)
GROUP BY state, city WITH ROLLUP

统计payments表付款方式的总额
SELECT
pm.payment_method_id,
SUM(p.amount) AS total
FORM payments p
JOIN payments_method pm
ON p.payment_method = pm.payment_method_id
GROUP BY pm.name WITH ROLLUP