问题描述
我有一个名为 company_emp 的表.在该表中，我有 6 列与员工相关:
I have table called company_emp. In that table I have 6 columns related to employees:
- empid
- 名字
- dob
- 司法部，...
我有另一个表叫做 bday.因为我只有 2 列；empid 和 dob.
I have another table called bday. In that I have only 2 columns; empid and dob.
我有这个查询:
select empid, dob
from company_emp
where dob like '01/05/2011'
它显示了一些员工列表.
It shows some list of employees.
以同样的方式我用表 bday 查询它列出了一些员工.
In the same way I have queried with table bday it listed some employees.
现在我想为日期为01/05/2011"的员工更新 company_emp 表.
Now I want to update the company_emp table for employees who have date '01/05/2011'.
我试过这样的查询:
update company_name a
set dob = (select dob from bday b
where b.empid=a.empid
and to_char(a.dob,'dd/mm/yyyy') = '01/05/2011'}
然后该行中的所有记录都变为空.如何修复此查询?
Then all the records in that row becoming null. How can I fix this query?
推荐答案
您正在更新 company_name/emp 表中的每一行.
You're updating every row in the company_name/emp table.
您可以使用相关子查询修复该问题以确保该行存在，或者通过在 bday.empid 上放置主键或唯一键并进行查询来更有效:
You can fix that with a correlated subquery to make sure the row exists, or more efficiently by placing a primary or unique key on bday.empid and querying:
update (
select c.dob to_dob,
d.dob from_dob
from company_emp c join dob d on (c.empid = d.empid)
where d.dob = date '2011-05-01')
set to_dob = from_dob
语法未测试.
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