Yesterday we sent 12,000 ACH payments to the clearing bank, but its acknowledgment file only has 11,985, and the total amount is off by $38,000. Both sides are loaded into the database, each table holding payment ID and amount. How would you write SQL to pinpoint the differences, and how would you judge where the problem is?

昨天我们发给清算行 12,000 笔 ACH 付款，清算行的回执文件只有 11,985 笔，总金额还差了 $38,000。两边数据都已经导进数据库，各有一张表，记录付款编号和金额。你会怎么写 SQL 定位差异，又会怎么判断问题出在哪？