How can mysql add id as a self-increasing primary key to a table that has already been built?

This article introduces the relevant knowledge of "mysql how to add id to the established table as self-increasing primary key". In the actual case operation process, many people will encounter such difficulties. Next, let Xiaobian lead you to learn how to deal with these situations! I hope you can read carefully and learn something!

Add id to self-increasing primary key in the created table without primary key:

alter table TABLE_NAME add id int not null primary key Auto_increment

There is no primary key in the original table, and the modified table already has a primary key:

alter table TABLE_NAME add primary key(COL_NAME);

There is a primary key in the original table. If you want to modify other columns as primary keys, you need to delete the original primary key first, and then modify other columns as primary keys:

alter table TABLE_NAME drop primary key;

alter table TABLE_NAME add primary key(COL_NAME);

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