SQL通过id从另一个表中检索值并显示总数

Question

通过id从另一个表中检索值并显示总数（通过获取id并根据id从table2获取值来迭代table1）

场景 - 获取发票ID 987的总和

pid金额在表2中，我想得到总数987

表1 view


表2 view

Answer 1

Try this -

$sql = "SELECT SUM(t1.Amount) FROM t1 LEFT JOIN e1 ON t1.PID = e1.PID WHERE e1.InvoiceID='987' GROUP BY e1.InvoiceID";

Answer 2

SELECT a.id, sum(b.amount)
FROM e1 a
INNER JOIN t1 b ON a.pid = b.pid
group by a.id;