Update

---

Note: Make sure to read the Getting Started, Demo Schema and Cursor first, as it is essential for better understanding of this tutorial.

---

pgcrud has one function to perform synchronous update operations:

• pg.update_many: Updates multiple records.

And pgcrud has one function to perform asynchronous update operations:

• pg.async_update_many: Analogous to pg.update_many.

Function for single record updates do not exist because PostgreSQL UPDATE command does not inherently target a single record.

Parameters

• cursor (required): To execute the query.
• update (required): To specify which table to update.
• set_ (required): To assign new values to columns.
• from_ (optional): To specify tables for subqueries.
• where (optional): To determine which rows to update.
• returning (optional): To fetch the updated rows.
• additional_values (optional): Additional values that can be updated.
• no_fetch (optional): To execute only.[^1]

Cursor

The cursor parameter is explained in detail here.

Update

The update parameter specifies which table to update. It expects an identifier as input.

syncasync

import pgcrud as pg
from pgcrud import Identifier as i


def update_book(
        cursor: pg.Cursor,
        id_: int,
        title: str,
) -> None:

    pg.update_many(
        cursor=cursor,
        update=i.book,
        set_=(i.title, title),
        where=i.id == id_, 
    )

import pgcrud as pg
from pgcrud import Identifier as i


async def update_book(
        cursor: pg.AsyncCursor,
        id_: int,
        title: str,
) -> None:

    await pg.async_update_many(
        cursor=cursor,
        update=i.book,
        set_=(i.title, title),
        where=i.id == id_, 
    )

Set

The set parameter expects a tuple containing two items: the first item is either a single identifier or a sequence of identifiers that specify the columns to be updated, while the second item can be a single value, a sequence of values, or a model instance.

syncasync

from datetime import date

from pydantic import BaseModel

import pgcrud as pg
from pgcrud import Identifier as i


class AuthorUpdate(BaseModel):
    name: str
    date_of_birth: date


def update_author(
        cursor: pg.Cursor,
        id_: int,
        update: AuthorUpdate,
) -> None:

        pg.update_many(
            cursor=cursor,
            update=i.book,
            set_=((i.name, i.date_of_birth), update),
            where=i.id == id_, 
        )

from datetime import date

from pydantic import BaseModel

import pgcrud as pg
from pgcrud import Identifier as i


class AuthorUpdate(BaseModel):
    name: str
    date_of_birth: date


async def update_author(
        cursor: pg.AsyncCursor,
        id_: int,
        update: AuthorUpdate,
) -> None:

        await pg.async_update_many(
            cursor=cursor,
            update=i.book,
            set_=((i.name, i.date_of_birth), update),
            where=i.id == id_, 
        )

From

Where

The where parameter is used to specify conditions for updating records. It accepts a comparison expression as its input. This can be a single comparison expression or an intersection or union of expressions.

syncasync

from datetime import date

import pgcrud as pg
from pgcrud import Identifier as i


def update_book(
        cursor: pg.Cursor,
        author_id: int,
        title: str,
        publication_date: date,
):

    pg.update_many(
        cursor=cursor,
        update=i.book,
        set_=(i.publication_date, publication_date),
        where=(i.title == title) & (i.author_id == author_id),
    )

from datetime import date

import pgcrud as pg
from pgcrud import Identifier as i


async def update_book(
        cursor: pg.AsyncCursor,
        author_id: int,
        title: str,
        publication_date: date,
):

    await pg.async_update_many(
        cursor=cursor,
        update=i.book,
        set_=(i.publication_date, publication_date),
        where=(i.title == title) & (i.author_id == author_id),
    )

Returning

The returning parameter is used to retrieve the record after update. The returning parameter expects a single or multiple expressions as input.

Additional Values

No Fetch