In MySQL, how to specify that an existing user name can only access one or more databases, and other database restrictions cannot be accessed

Question 1: Title, just want to let the specified user name read authorization of the specified database, how to implement it?
Question 2: There are many members of the site, there are now want to outsource some of the site features to third-party companies to do, but I do not want to open member data to them, how to control the membership table or the core table specified access to the specified data, such as the membership table can only access testuser1, TESTUSER2, etc.

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Question 1: Title, just want to let the specified user name read authorization of the specified database, how to implement it?
Question 2: There are many members of the site, there are now want to outsource some of the site features to third-party companies to do, but I do not want to open member data to them, how to control the membership table or the core table specified access to the specified data, such as the membership table can only access testuser1, TESTUSER2, etc.

You create a MySQL account, assign permissions to the account, and specify what tables can be written.

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