Insert and update with core SQLAlchemy
As you can see from the SQLAlchemy Overview documentation, sqlalchemy is build with two layers: ORM
and Core
. Currently you are using only some constructs of the Core
and building everything manually.
In order to use Core
you should let SQLAlchemy know some meta information about your database in order for it to operate on it. Assuming you have a table mytable
with columns field1, field2, field3
and a defined primary key
, the code below should perform all the tasks you need:
from sqlalchemy.sql import table, column, select, update, insert
# define meta information
metadata = MetaData(bind=engine)
mytable = Table('mytable', metadata, autoload=True)
# select
s = mytable.select() # or:
#s = select([mytable]) # or (if only certain columns):
#s = select([mytable.c.field1, mytable.c.field2, mytable.c.field3])
s = s.where(mytable.c.field1 == 'abc')
result = session.execute(s)
out = result.fetchall()
print(out)
# insert
i = insert(mytable)
i = i.values({"field1": "value1", "field2": "value2"})
session.execute(i)
# update
u = update(mytable)
u = u.values({"field3": "new_value"})
u = u.where(mytable.c.id == 33)
session.execute(u)
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Jester
Updated on July 23, 2022Comments
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Jester almost 2 years
I have a database that I don't have metadata or orm classes for (the database already exists).
I managed to get the select stuff working by:
from sqlalchemy.sql.expression import ColumnClause from sqlalchemy.sql import table, column, select, update, insert from sqlalchemy.ext.declarative import * from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine import pyodbc db = create_engine('mssql+pyodbc://pytest') Session = sessionmaker(bind=db) session = Session() list = [] list.append (column("field1")) list.append (column("field2")) list.append (column("field3")) s = select(list) s.append_from('table') s.append_whereclause("field1 = 'abc'") s = s.limit(10) result = session.execute(s) out = result.fetchall() print(out)
So far so good.
The only way I can get an update/insert working is by executing a raw query like:
session.execute(<Some sql>)
I would like to make it so I can make a class out of that like:
u = Update("table") u.Set("file1","some value") u.Where(<some conditon>) seasion.execute(u)
Tried (this is just one of the approaches I tried):
i = insert("table") v = i.values([{"name":"name1"}, {"name":"name2"}]) u = update("table") u = u.values({"name": "test1"})
I can't get that to execute on:
session.execute(i)
or
session.execute(u)
Any suggestion how to construct an insert or update without writing ORM models?
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Jester over 10 yearsAfter searching for 2 days found most of that also anyway tanks for clearint it up for me
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Aidis almost 7 yearsWhy session and not transaction? From docs, session should be used with ORM, right?