txtSQL has been designed to allow the use of primary keys. There are two ways to add them, and only one way to drop them.

To add primary keys when creating a table, specify the column type 'primary' and set it equal to 1. The column must be 'int' (integer) and 'auto_increment'.
The other way to add a primary key is to use the altertable() function.

If you want to drop a primary key, you must also use the altertable() function.