Personally, I tend to use the session interface in SqlAlchemy to do my queries: http://www.sqlalchemy.org/docs/ormtutorial.html

Normally, to do a select all, you’d do something like this:

But yes, I do need to write another tutorial on SqlAlchemy that goes over existing database interfacing, among other things. Thanks for the readership!

- Mike

Starting to learn SQLAlchemy. About your comment that you can connect to previously created tables, I noticed that every SQLAlchemy I found so far has an example like you wrote, ie create the table and then go from there, but none where an already existing table on an Oracle database for example is used.

My question is: Do I need to create the metadata for an existing table I want to use in order to be able to select the data from it? Here’s a test script I tried to run with an already existing table:

———-
#!/usr/bin/env python

from sqlalchemy import create_engine
from sqlalchemy import Table, Column, Integer, String, MetaData, ForeignKey
from sqlalchemy.sql import select

engine = create_engine(‘oracle://myconnectioninfohere’, echo=True)

metadata = MetaData()

myTable = Table(‘microschargement’, metadata, autoload_with=engine)

conn = engine.connect()

mySelect = select([myTable])
print mySelect

myDataSet = conn.execute(mySelect)

for row in myDataSet:
print row
———-

It doesn’t work. The result from the “print mySelect” statement gives me:

“select from microschargement”

and I expected:

“select * from microschargement”

Of course, when I reach the “execute(mySelect) statement, the program crashes.

Could you add a little bit of info on how to access the data from an already created table? It would be much appreciated.

- Mike

Thank you for the tutorial.

I’ve got “ArgumentError: columns argument to select() must be a Python list or other iterable
” while executing “select(and_(users_table.c.name==”Martha”, users_table.c.age < 25))"

If I replace it by "select([users_table], and_(users_table.c.name=="Martha", users_table.c.age < 25))" then it works fine.

Thank you for the tutorial.

I’ve got “ArgumentError: columns argument to select() must be a Python list or other iterable
” while executing “select(and_(users_table.c.name==”Martha”, users_table.c.age < 25))"

If I replace it by "select([users_table], and_(users_table.c.name=="Martha", users_table.c.age < 25))" then it works fine.

I changed the query in this post to use an equality check rather than using “like” since that seemed to be causing me issues.

- Mike

I changed the query in this post to use an equality check rather than using “like” since that seemed to be causing me issues.

- Mike