Does not update the column with the "update" clause

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Does not update the column with the "update" clause

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#1 by (1 votes)

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I am trying to apply this update from record to table, it does not generate an error, but it does not execute the update either, when doing the table query it does not make the changes. I appreciate help.

while True:

    opcionMenu = input("inserta un numero valor >> ")
    try:
        opcionMenu = str(opcionMenu)
    except:
        pass
    else:
        if opcionMenu == "A":
            print("Has pulsado la Opcion Modificar Numero de Documento Empleado")
            numdocEmp = int(input("Digite el idCodigo del Empleado a Modificar :"))
            nuevonumdocEmp = int(input("Digite el Nuevo numero de Docuemnto del Empleado a Modificar :"))

            nuevo = ("update(Empleados).where(numdocEmp == '%S').values(nuevonumdocEmp)")

            session.flush(nuevo)
            session.commit()
            break

python sqlalchemy

asked by Jsierra2017 23.12.2017 в 18:19

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1 answer

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score 1 · Answer 1

There are several ways to update a table, using sqlalchemy.update you can do the following:

from sqlalchemy import update

if opcionMenu == "A":
    print("Has pulsado la Opcion Modificar Numero de Documento Empleado")
    numdocEmp = int(input("Digite el idCodigo del Empleado a Modificar :"))
    nuevonumdocEmp = int(input("Digite el Nuevo numero de Docuemnto del Empleado a Modificar :"))

    stmt = update(Empleado)\
        .where(Empleado.numdocEmp == numdocEmp)\
        .values(numdocEmp = nuevonumdocEmp)
    session.execute(stmt)
    session.commit()

Where Empleado is your mapped base class, whose instances form the rows of your empleados table.

Another very simple option if you use the declarative system is to obtain the row or rows with query and then simply modify the attributes you want:

Loading the objects:

if opcionMenu == "A":
    print("Has pulsado la Opcion Modificar Numero de Documento Empleado")
    numdocEmp = int(input("Digite el idCodigo del Empleado a Modificar :"))
    nuevonumdocEmp = int(input("Digite el Nuevo numero de Docuemnto del Empleado a Modificar :"))

    rows = session.query(Empleado).filter(Empleado.numdocEmp == numdocEmp)
    if rows:
        for row in rows:
            row.numdocEmp = nuevonumdocEmp
        session.commit()
    else:
        print("Número no encontrado")

In this case it is assumed that only one row with that value will exist, however you can iterate over the whole result instead of using first() if this is not the case.

Directly on the database (using the method update of query ):

if opcionMenu == "A":
    print("Has pulsado la Opcion Modificar Numero de Documento Empleado")
    numdocEmp = int(input("Digite el idCodigo del Empleado a Modificar :"))
    nuevonumdocEmp = int(input("Digite el Nuevo numero de Docuemnto del Empleado a Modificar :"))

    session.query(Empleado)\
        .filter(Empleado.numdocEmp==numdocEmp)\
        .update({"numdocEmp": nuevonumdocEmp})
    session.commit()

As a point, when debugging this type of "silent" problems, it is often helpful to specify the parameter echo as True when declaring the engine of the database:

engine = create_engine('sqlite:///myexampledb.db', echo=True)

This allows us to see by console in quite detail all the interactions between SQLAlchemy and the database itself.