在sqlite3中读回日期时间

Question

I am using Python to create an in-memory sqlite3 database with a timestamp column. When I use min() or max() on this column in my query, the column is returned as a string rather than a Python datetime object. I read a previous question on Stackoverflow that provided a solution for normal SELECT statements, but it doesn't work if max() or min() is used. Here's an example:

>>> 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 0x7eff420e0be0>
>>> c.execute('insert into foo values(?, ?)', (23, datetime.datetime.now()))
<sqlite3.Cursor object at 0x7eff420e0be0>
>>> c.execute('select * from foo')
<sqlite3.Cursor object at 0x7eff420e0be0>
>>> c.fetchall()
[(23, datetime.datetime(2010, 12, 14, 1, 15, 54, 685575))]
>>> c.execute('select max(baz) from foo')
<sqlite3.Cursor object at 0x7eff420e0be0>
>>> c.fetchall()
[(u'2010-12-14 01:15:54.685575',)]

I tried to cast the result to a timestamp but it only returns the year:

>>> c.execute('select cast(max(baz) as timestamp) from foo')
<sqlite3.Cursor object at 0x7eff420e0be0>
>>> c.fetchall()
[(2010,)]

Is there any way to fetch a proper datetime object, without manually converting the string using datetime.strptime() after fetching it?

Answer 1

You have to set detect_types to sqlite.PARSE_COLNAMES and use as "foo [timestamp]" like this:

import sqlite3
import datetime

db = sqlite3.connect(':memory:', detect_types = sqlite3.PARSE_COLNAMES)
c = db.cursor()
c.execute('create table foo (bar integer, baz timestamp)')
c.execute('insert into foo values(?, ?)', (23, datetime.datetime.now()))
c.execute('insert into foo values(?, ?)', (42, datetime.datetime.now() + datetime.timedelta(-1)))
c.execute('select bar, baz as "ts [timestamp]" from foo')
print c.fetchall()
c.execute('select max(baz) as "ts [timestamp]" from foo')
print c.fetchall()

Did a nice little Google search and found this message .