How to read datetime back from sqlite as a datetim

Question

I'm using the sqlite3 module in Python 2.6.4 to store a datetime in a SQLite database. Inserting it is very easy, because sqlite automatically converts the date to a string. The problem is, when reading it it comes back as a string, but I need to reconstruct the original datetime object. How do I do this?

Answer 1

It turns out that sqlite3 can do this and it's even documented, kind of - but it's pretty easy to miss or misunderstand.

What I had to do is:

• Pass the sqlite3.PARSE_COLNAMES option in the .connect() call, eg.

conn = sqlite3.connect(dbFilePath, detect_types=sqlite3.PARSE_DECLTYPES|sqlite3.PARSE_COLNAMES)

• Put the type I wanted into the query - and for datetime, it's not actually "datetime", but "timestamp":

  sql = 'SELECT jobid, startedTime as "[timestamp]" FROM job'
  
  cursor = conn.cursor()
  try:
      cursor.execute(sql)
      return cursor.fetchall()
  finally:
      cursor.close()
  

If I pass in "datetime" instead it's silently ignored and I still get a string back. Same if I omit the quotes.

Answer 2

If you declare your column with a type of timestamp, you're in clover:

>>> db = sqlite3.connect(':memory:', detect_types=sqlite3.PARSE_DECLTYPES)
>>> c = db.cursor()
>>> c.execute('create table foo (bar integer, baz timestamp)')
<sqlite3.Cursor object at 0x40fc50>
>>> c.execute('insert into foo values(?, ?)', (23, datetime.datetime.now()))
<sqlite3.Cursor object at 0x40fc50>
>>> c.execute('select * from foo')
<sqlite3.Cursor object at 0x40fc50>
>>> c.fetchall()
[(23, datetime.datetime(2009, 12, 1, 19, 31, 1, 40113))]

See? both int (for a column declared integer) and datetime (for a column declared timestamp) survive the round-trip with the type intact.

Answer 3

Note: In Python3, I had to change the SQL to something like:

SELECT jobid, startedTime as "st [timestamp]" FROM job

(I had to explicitly name the column.)