Creating multiple references in databases for same foreign key

[aamir-alii]

Issue Creation Checklist

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Add upper case table name in code and dialect server is using lower_case_table_names the issue will be generated.

Bug Description

If I use database name in uppercase and my server is configured with lower_case_table_names then when I specify any relation in my code and the sync option with alter true is on it will create multiple references in table.

Reproducible Example

These all references are created for same reference

What do you expect to happen?

There should be only one reference for each reference

What is actually happening?

There is always creating a new reference each time code restart and sync with alter true is on,

Environment

• Sequelize version: 6.37.2
• Node.js version: 20.12.0
• Database & Version: MYSQL Server 8
• Connector library & Version: mysql2@3.9.3

Would you be willing to resolve this issue by submitting a Pull Request?

• Yes, I have the time and I know how to start.
• Yes, I have the time but I will need guidance.
• No, I don't have the time, but my company or I are supporting Sequelize through donations on OpenCollective.
• No, I don't have the time, and I understand that I will need to wait until someone from the community or maintainers is interested in resolving my issue.

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[ephys]

Note for when someone starts working on this task: there are some information about this in #17256

[aamir-alii]

What if we delete all the constraint of particular table before hand as it is already creating that constraint again look into following code.

[ephys]

sync cannot delete anything unless force is specified, in which case it deletes everything

[aamir-alii]

sync cannot delete anything unless force is specified, in which case it deletes everything

you don't get my point I want to do something like this

[aamir-alii]

Other thing that I have noticed that If we remove reference from a field (and it is still in the model mean we don't remove the field but just the references) it reference in database will not be removed as we are only removing constraint from the field which have some references in the code.

[ephys]

To explain what I meant in my previous comment: removing constraints is a destructive operation, and the base sync does not do that. I see that in your initial comment you mentioned using the alter option, which could do this kind of operation

[aamir-alii]

What about if we add name constraint and check if it is not exist with that name and drop if exists
adding name constraint

searching for name constraint