Question

I created a table by following query:

with sqlite3.connect('example.db', detect_types=sqlite3.PARSE_DECLTYPES) as conn:
    cur = conn.cursor()
    cur.execute("CREATE TABLE Surveys(Id INTEGER PRIMARY KEY, Name TEXT, Desc TEXT, DictObject BLOB, Hash TEXT)")
    conn.commit()

Now I have to add some Survey data to Surveys table for every request. Surveys table has Id as primary integer value. This has to be increased upon every insertion – And What is the proper way to do it? Do I have to fetch every row and check what the lastIdis upon every request?

Answer 1

sqlite will automatically provide an id for a INTEGER PRIMARY KEY column on INSERT on a table if you do not provide a value yourself. Just insert data for every column except for the id column.

with sqlite3.connect('example.db', detect_types=sqlite3.PARSE_DECLTYPES) as conn:
    cur = conn.cursor()
    cur.execute("INSERT INTO Surveys(Name, Desc, DictObject, Hash) VALUES (?, ?, ?, ?",
        ('somename', 'some description\nof sorts\n',
         "{'dump': 'of a dictionary'}", '0xhash'))

You may want to add the keyword AUTOINCREMENT to your id column though; the default is to pick the highest existing row id plus 1, and if you delete data from the table on a regular basis that can lead to reuse of ids (delete the current highest id and it’ll be re-used next time round). AUTOINCREMENT guarantees that each generated number will only be used once for a table, independent of deletes.

Note that when you use a sqlite3 connection as a context manager (using the with statement), the commit() is automatically applied for you. Quoting the documentation:

Connection objects can be used as context managers that automatically commit or rollback transactions. In the event of an exception, the transaction is rolled back; otherwise, the transaction is committed.

In other words, you can safely remove the conn.commit() line in your code, it is entirely redundant.