MySQL ALTER COLUMN type關於「MySQL PRIMARY key multiple columns」標籤，搜尋引擎有相關的訊息討論：
Multi-Column Primary Key in MySQL 5 - Stack Overflowstackoverflow.com › questions › multi-column-primary-ke...How to set up multiple fields as primary key in MySQL?dba.stackexchange.com › questions › how-to-set-up-multi...How can we set PRIMARY KEY on multiple columns of an exi