Postgres -更改列数据

Question

有一个问题，在更新表‘佣金’中的一些行。现在我有了像commission_number /123/456这样的bar。我想把它重命名为John/123/456等，从'user‘表中取一个名字

commission                       user
-------------------------        -----------------
commission_number|user_id         username|user_id
-------------------------        -----------------
bar/123/456      | 1               John   | 1
bar/123/123      | 2               Bob    | 2
bar/456/123      | 3               Thomas | 3

下面是我的查询，使用'baz‘。但是不知道如何从'user‘表中放置'username’。我只需要替换'baz'，并使用用户名从'user'，但不知道如何。

UPDATE commission
SET commission_number = overlay(commission_number placing 'baz' FROM POSITION('bar' IN commission_number) for 3)
WHERE commission_number in (1,2,3,4,5,6,7,8)

Answer 1

我会从实验开始，比如..。

UPDATE commission
SET commission_number = 
  (SELECT UserName FROM User WHERE user.user_id=commission.user_id)
   ||SubString(commission_number,4,8000)

除了前3个字符之外，还有right(commission_number,-3)可以从中获取所有字符。

我不知道你想要做什么

WHERE commission_number in (1,2,3,4,5,6,7,8)？

Answer 2

update commission 
   set commission_number = u.username || '/' || left(commission_number, -strpos(commission_number, '/'))
from users u
  where u.user_id = commission.user_id

Answer 3

这说明了数据在更新后的外观。在处理字符串函数时，我经常使用这种select语句。

select c.commission_number, c.user_id, 
       (select username 
        from "user" 
        where "user".user_id = c.user_id) username,
       overlay(c.commission_number 
               placing (select username 
                        from "user" 
                        where "user".user_id = c.user_id) 
               from 1 for 3)
from commission c;

现在，您可以使用您知道可以工作的术语来编写update语句。

update commission 
set commission_number = overlay(commission_number 
                                placing (select username 
                                         from "user" 
                                         where "user".user_id = commission.user_id) 
                                from 1 for 3);