我们需要有关无法正常工作的详细信息，但我认为您只需要使用:

We need details about what's not working, but I think you only need to use:

UPDATE TablePeople 
   SET missingdate = (SELECT MAX(te.replacementDate)
                        FROM TABLEEVENT te
                       WHERE te.people_id = TablePeople.id)   
 WHERE missingdate IS NULL

注释

• 由于担心您会从子查询中获取多个值，因此使用MAX来返回最新的替换日期
• 如果TABLEEVENT中没有支持记录，则它将返回null，因此没有变化

Notes

• MAX is being used to return the latest replacementdate, out of fear of risk that you're getting multiple values from the subquery
• If there's no supporting record in TABLEEVENT, it will return null so there's no change