由于更改而更新数据库中的现有记录？

Question

Database tables:

task_assignee

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| id | task_id | assignee_id |
------------------------------
| 1  |    3    |       2     |  
| 2  |    3    |       5     |

task

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| id | content | category |
---------------------------
| 3  | 'Bake'  |   'A'    |

Here is the scenario:

1. I create a task with two assignees. That's equal to two records in task_assignee for that task. I save the task.
2. I want to edit the task and remove one of the two assignees and then select someone else. So, still equal to two assignees, just one of them now different.

What would be the most efficient way to make these changes to the database?

I'm thinking of adding another column to task_assignee that will serve as a flag of sorts that I will update. I will set it to 0 if the assignee is unselected, 1 if it is selected, but I'm not sure if that'd be a good thing to do, and I don't think that can cover when new assignees are selected. What I can think of is a tedious loop that will check if the new assignee selected for that task is already in task_assignee and if it is already attached to that task, if it isn't then it inserts a new one.

I also thought of just deleting the past records first then insert the new ones, but I'm not sure if that's efficient? -> When adding a new assignee

Answer 1

Isn't it just more simple to delete the record in task_assignee from the user you want to remove from the task and add the one you want to add. So you only need two queries. Delete from and insert into.

You should keep the tables as clean as possible and since the task_assignee table has no unique id you can delete all the records you don't need.

As said above you can also do the update method. I'm more a fan of deleting and adding it in again. Just a force of habit.

kind regards