MySQL design for associated IDs

I'm new to programming so forgive my simple questions.

Basically, I have two different tables containing data related to one another. I'd like to create a new column called "id" which will associate rows in both tables so that I can appropriately display the data.

When a user takes an action, a row is inserted into both tables.

What kind of properties should "id" have? Primary key, auto-increment on both tables or one table? How do I ensure that the same ID is inserted into both 开发者_C百科rows, do I insert into table1 first, then grab that ID and insert into table2?

Any help appreciated. Thanks

It's somewhat difficult to answer your question without knowing what the two tables contain, but I suggest you read about database normalization.

Regardless of how many tables you decide to have, each table should have an id column of some sort. Having a way to uniquely refer to a single row makes life a lot easier down the road when you need to make changes to the data. Auto-increment saves you from having to come up with your own unique primary key values.