If you never want to have duplicates, you should declare this as a table constraint: CREATE TABLE bookmarks( users_id INTEGER, lessoninfo_id INTEGER, UNIQUE(users_id, lessoninfo_id) ); (A primary key over both columns would have the same effect.) It is then possible to tell the database that you want to silently ignore records that would violate such … Read more
In windows you can try this program http://www.nirsoft.net/utils/opened_files_view.html to find out the process is handling db file. Try closed that program for unlock database In Linux and macOS you can do something similar, for example, if your locked file is development.db: $ fuser development.db This command will show what process is locking the file: > … Read more
check is a keyword in SQL. Rename that column.
I’m guessing from what little you have written that you want a variable list of fields (where the list of fields is retrieved from tableB) to be retrieved from tableA. This isn’t possible directly in SQL. You will need to make 2 calls, the first one to retrieve the list of fields, and the second … Read more