Creating primary key on two columns

I am using SQLite GUI Browser to work with the database. I can't find any button to make primary key on two or mor开发者_开发问答e columns. How to do this?

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SQLite does not support adding a constraint.

You have to create a new table, specifying its whole column structure, and import old data into the new table. Then remame the new one, after having dropped the old one.