1.分析
①列名直接计算
②子查询时where 条件中，如果是用 = 报错，用 in 就可以了？？？

2.代码

# 子查询：
UPDATE salaries
SET salary = salary * 1.1
WHERE emp_no in (SELECT emp_no FROM emp_bonus)
and salaries.to_date = '9999-01-01'

# join两张表：
update salaries as s join emp_bonus as e on s.emp_no=e.emp_no
set salary=salary*1.1
where to_date='9999-01-01'