update a joined table with sqlalchemy core

upd = table1.update()\
   .values(id = table2.c.id)\
   .where(table1.c.name == table2.c.name)

Suggestion : 2

The join() method returns a join object from one table object to another.,In this chapter, we will learn how to use Joins in SQLAlchemy.,Effect of joining is achieved by just placing two tables in either the columns clause or the where clause of the select() construct. Now we use the join() and outerjoin() methods.,If this statement is executed using the connection representing engine, data belonging to selected columns will be displayed. The complete code is as follows −

The join() method returns a join object from one table object to another.

join(right, onclause = None, isouter = False, full = False)

For example, following use of join() method will automatically result in join based on the foreign key.

>>> print(students.join(addresses))

This is equivalent to following SQL expression −

students JOIN addresses ON students.id = addresses.st_id

If we now build the below select construct using this join as −

stmt = select([students]).select_from(j)

This will result in following SQL expression −

SELECT students.id, students.name, students.lastname
FROM students JOIN addresses ON students.id = addresses.st_id

Suggestion : 3

Last Updated : 31 Jan, 2022

Updating table elements have a slightly different procedure than that of a conventional SQL query which is shown below

from sqlalchemy
import update
upd = update(tablename)
val = upd.values({
   "column_name": "value"
})
cond = val.where(tablename.c.column_name == value)

Suggestion : 4

Joins in SQLAlchemy can be implemented using the .join() method. But if there is a requirement to join tables based on multiple conditions, you can also do that in SQLAlchemy passing conditions inside join().,We are using and_ operator from SQLAlchemy in the first query where the query will join the tables based on both conditions true but in or_ case the joining of the tables will depend on at least one condition match,Apply join based on multiple conditions SQLAlchemy,Apply condition based multiple filters in SQLAlchemy

from sqlalchemy
import or_, and_

#USING AND CONDITION
session.query(
   EmployeeModel.name,
   EmployeeDepartment.dept_name
).join(
   EmployeeDepartment,
   and_(
      EmployeeDepartment.employee_id == EmployeeModel.id,
      EmployeeDepartment.dept_code == 'P01'
   )
).all()

#USING OR CONDITION
session.query(
   EmployeeModel.name,
   EmployeeDepartment.dept_name
).join(
   EmployeeDepartment,
   or_(
      EmployeeDepartment.employee_id == EmployeeModel.id,
      EmployeeDepartment.dept_code == 'P01'
   )
).all()

In the code snippet, we are joining two tables employee and employee_department using two conditions:

EmployeeDepartment.employee_id == EmployeeModel.id,
   EmployeeDepartment.dept_code == 'P01'