sqlmodel/docs/tutorial/update.md

Update Data - UPDATE

Now let's see how to update data using SQLModel.

Continue From Previous Code

As before, we'll continue from where we left off with the previous code.

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{!./docs_src/tutorial/where/tutorial006.py!}

Remember to remove the database.db file before running the examples to get the same results.

Update with SQL

Let's quickly check how to update data with SQL:

UPDATE hero
SET age=16
WHERE name = "Spider-Boy"

This means, more or less:

Hey SQL database 👋, I want to UPDATE the table called hero.

Please SET the value of the age column to 16...

...for each of the rows WHERE the value of the column name is equal to "Spider-Boy".

In a similar way to SELECT statements, the first part defines the columns to work with: what are the columns that have to be updated and to which value. The rest of the columns stay as they were.

And the second part, with the WHERE, defines to which rows it should apply that update.

In this case, as we only have one hero with the name "Spider-Boy", it will only apply the update in that row.

!!! info Notice that in the UPDATE the single equals sign (=) means assignment, setting a column to some value.

And in the `WHERE` the same single equals sign (`=`) is used for **comparison** between two values, to find rows that match.

This is in contrast to Python and most programming languages, where a single equals sign (`=`) is used for assignment, and two equal signs (`==`) are used for comparisons.

You can try that in DB Browser for SQLite:

After that update, the data in the table will look like this, with the new age for Spider-Boy:

id	name	secret_name	age
1	Deadpond	Dive Wilson	null
2	Spider-Boy	Pedro Parqueador	16 ✨
3	Rusty-Man	Tommy Sharp	48

!!! tip It will probably be more common to find the row to update by id, for example:

```SQL
UPDATE hero
SET age=16
WHERE id = 2
```

But in the example above I used `name` to make it more intuitive.

Now let's do the same update in code, with SQLModel.

To get the same results, delete the database.db file before running the examples.

Read From the Database

We'll start by selecting the hero "Spider-Boy", this is the one we will update:

# Code above omitted 👆

{!./docs_src/tutorial/update/tutorial001.py[ln:44-49]!}

# Code below omitted 👇

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{!./docs_src/tutorial/update/tutorial001.py!}

Let's not forget to add that update_heroes() function to the main() function so that we call it when executing the program from the command line:

# Code above omitted 👆

{!./docs_src/tutorial/update/tutorial001.py[ln:58-65]!}

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{!./docs_src/tutorial/update/tutorial001.py!}

Up to that point, running that in the command line will output:

$ python app.py

// Some boilerplate and previous output omitted 😉

// The SELECT with WHERE
INFO Engine SELECT hero.id, hero.name, hero.secret_name, hero.age 
FROM hero 
WHERE hero.name = ?
INFO Engine [no key 0.00017s] ('Spider-Boy',)

// Print the hero as obtained from the database
Hero: name='Spider-Boy' secret_name='Pedro Parqueador' age=None id=2

!!! tip Notice that by this point, the hero still doesn't have an age.

Set a Field Value

Now that you have a hero object, you can simply set the value of the field (the attribute representing a column) that you want.

In this case, we will set the age to 16:

# Code above omitted 👆

{!./docs_src/tutorial/update/tutorial001.py[ln:44-51]!}

# Code below omitted 👇

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{!./docs_src/tutorial/update/tutorial001.py!}

Add the Hero to the Session

Now that the hero object in memory has a change, in this case a new value for the age, we need to add it to the session.

This is the same we did when creating new hero instances:

# Code above omitted 👆

{!./docs_src/tutorial/update/tutorial001.py[ln:44-52]!}

# Code below omitted 👇

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{!./docs_src/tutorial/update/tutorial001.py!}

Commit the Session

To save the current changes in the session, commit it.

This will save the updated hero in the database:

# Code above omitted 👆

{!./docs_src/tutorial/update/tutorial001.py[ln:44-53]!}

# Code below omitted 👇

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{!./docs_src/tutorial/update/tutorial001.py!}

It will also save anything else that was added to the session.

For example, if you were also creating new heroes and had added those objects to the session before, they would now be saved too in this single commit.

This commit will generate this output:

$ python app.py

// Some boilerplate output omitted 😉

// Previous output omitted 🙈

// The SQL to update the hero in the database
INFO Engine UPDATE hero SET age=? WHERE hero.id = ?
INFO Engine [generated in 0.00017s] (16, 2)
INFO Engine COMMIT

Refresh the Object

At this point, the hero is updated in the database and it has the new data saved there.

The data in the object would be automatically refreshed if we accessed an attribute, like hero.name.

But in this example we are not accessing any attribute, we will only print the object. And we also want to be explicit, so we will .refresh() the object directly:

# Code above omitted 👆

{!./docs_src/tutorial/update/tutorial001.py[ln:44-54]!}

# Code below omitted 👇

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{!./docs_src/tutorial/update/tutorial001.py!}

This refresh will trigger the same SQL query that would be automatically triggered by accessing an attribute. So it will generate this output:

$ python app.py

// Some boilerplate output omitted 😉

// Previous output omitted 🙈

// The SQL to SELECT the fresh hero data
INFO Engine SELECT hero.id, hero.name, hero.secret_name, hero.age 
FROM hero 
WHERE hero.id = ?
INFO Engine [generated in 0.00018s] (2,)

Print the Updated Object

Now we can just print the hero:

# Code above omitted 👆

{!./docs_src/tutorial/update/tutorial001.py[ln:44-55]!}

# Code below omitted 👇

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{!./docs_src/tutorial/update/tutorial001.py!}

Because we refreshed it right after updating it, it has fresh data, including the new age we just updated.

So, printing it will show the new age:

$ python app.py

// Some boilerplate output omitted 😉

// Previous output omitted 🙈

// Print the hero with the new age
Updated hero: name='Spider-Boy' secret_name='Pedro Parqueador' age=16 id=2

Review the Code

Now let's review all that code:

{!./docs_src/tutorial/update/tutorial002.py!}

{!./docs_src/tutorial/update/annotations/en/tutorial002.md!}

!!! tip Check out the number bubbles to see what is done by each line of code.

Multiple Updates

The update process with SQLModel is more or less the same as with creating new objects, you add them to the session, and then commit them.

This also means that you can update several fields (attributes, columns) at once, and you can also update several objects (heroes) at once:

# Code above omitted 👆

{!./docs_src/tutorial/update/tutorial004.py[ln:44-70]!}

# Code below omitted 👇

{!./docs_src/tutorial/update/annotations/en/tutorial004.md!}

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{!./docs_src/tutorial/update/tutorial004.py!}

!!! tip Review what each line does by clicking each number bubble in the code. 👆

Recap

Update SQLModel objects just as you would with other Python objects. 🐍

Just remember to add them to a session, and then commit it. And if necessary, refresh them.