GROUP BY 子句

根据client_id分别统计每个client的总计销售金额
SELECT
client_id,
SUM(invoice_total) AS total_sales
FROM invoices
GROUP BY client_id

根据client_id分别统计每个client的总计销售金额,
并根据total_sales金额进行倒排序
SELECT
client_id,
SUM(invoice_total) AS total_sales
FROM invoices
GROUP BY client_id
ORDER BY total_sales DESC

根据client_id分别统计每个client的总计销售金额,
购买时间为2019后半年以后，
并根据total_sales金额进行倒排序
SELECT
client_id,
SUM(invoice_total) AS total_sales
FROM invoices
WHERE invoice_date >= ‘2019-07-01’
GROUP BY client_id
ORDER BY total_sales DESC

SELECT
date,
pm.name AS payment_method,
SUM(amount) AS total_payments
FROM payments p
JOIN payment_methods pm
ON p.payment_method = pm.payment_method_id
GROUP BY date
ORDER BY date