SQL Query question : how to add data to two tables connected by third Junction-table.

Question

Hello specialists.
Maybe this is the wrong formum but I've got a question for which you probably have the answer, i hope.
Situation
John is member of Group_A and Group_B
Bill is member of Group_B and Group_C
Allison is member of Group_A and Group_E
How can I create a query to input Allisons username into table 1 and groupmembership into table 2. Also updating the relationship within junction-table3 must be done automaticaly. I want to avoid duplicate records.
The final situation I want is given in red text.
The relationships between the tables are as follows
Table1 (PK)ID-Userinfo    [ONE]    <------------> [MANY] Table3 ID-Userinfo
Table3 (PK)ID-GroupInfo  [MANY] <------------> [ONE]   Table2 (PK)ID-GroupInfo
Table1: UserInfo
(PK)ID-Userinfo   UserName
1                        John
2                        Bill
3                        Allison
Table2: GroupInfo
(PK)ID-GroupInfo  GroupName
1                          Group_A
2                          Group_B
3                          Group_C
4                          Group_E
Table3: MemberOf
(PK)ID-MemberOf  ID-UserInfo  ID-GroupInfo
1                           1                 1
2                           1                 2
3                           2                 2
4                           2                 3
5                           3                 1
6                           3                 4
I hope you can help me cracking this nut.
Thx in advance. Greetings Fred

Answer 1

Hi RSingh
May i comment something very small?
Anyone who writes a response, done it on the assumption that he is writing the answer. Writing response is the statement of "I think that's correct". Each one that write a response see it as the answer. It makes no sense immediately mark your own
answer too (double actions). Marking a response as "Propose as answer" is explicitly designed to
allow others to announce that they think this is the best right answer in the thread, after the discussion :-)
In my personal opinion, we should not mark our own answers. There are enough users with permissions, which would be glad to mark your answers as correct / recommended.
Give us the opportunity, I will love to mark your answers :-). Moreover, by marking "Proposed as answer" you actually close the thread, other users which see that the question got an answer, may not check
the thread at all, and maybe they could provide a different answer.
* Exceptions are very specific cases. For example a case where the message has already become very old and no one marked anything. in this case marking "Proposed as answer" can help others and especially the person who ask the question, to focus
on thread and the answer (more on the subject is in the Moderators forum and the Moderators Guide by the way).
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