systems is data "<abbr title="also called marshalling, conversion">serialization</abbr>" which is taking data from the code (Python) and converting it into something that can be sent through the network. For example, converting an object containing data from a database into a JSON object. Converting `datetime` objects into strings, etc.

Another big feature needed by APIs is data validation, making sure that the data is valid, given certain parameters. For example, that some field is an `int`,...

	})
	return
}

// Having specify HAVING conditions for GROUP BY
//
//	// Select the sum age of users with name jinzhu
//	db.Model(&User{}).Select("name, sum(age) as total").Group("name").Having("name = ?", "jinzhu").Find(&result)
func (db *DB) Having(query interface{}, args ...interface{}) (tx *DB) {
	tx = db.getInstance()
	tx.Statement.AddClause(clause.GroupBy{
		Having: tx.Statement.BuildCondition(query, args...),

We might want to separate between installation and activation, it might be nice to allow a user to activate/deactivate a plugin instead of having to uninstall and reinstall a plugin in particular cases. This would prevent having to reconfigure the plugin again. For example it might be nice to turn off LDAP authentication without having to uninstall the plugin.

It also re-declares `id: int`. By doing this, we are making a **contract** with the API clients, so that they can always expect the `id` to be there and to be an `int` (it will never be `None`).

/// tip

Having the return model ensure that a value is always available and always `int` (not `None`) is very useful for the API clients, they can write much simpler code having this certainty.

/// note

FastAPI will know that the value of `q` is not required because of the default value `= None`.

Having `str | None` will allow your editor to give you better support and detect errors.

///

## Additional validation { #additional-validation }

	if err != nil {
		t.Fatalf("got error %v", err)
	}

	defer rows.Close()
	for rows.Next() {
		var name string
		var total int64
		rows.Scan(&name, &total)

		if name == users[0].Name && total != 3 {
			t.Errorf("Should have one user having name %v", users[0].Name)

}

func (c chainG[T]) Group(name string) ChainInterface[T] {
	return c.with(func(db *DB) *DB {
		return db.Group(name)
	})
}

func (c chainG[T]) Having(query interface{}, args ...interface{}) ChainInterface[T] {
	return c.with(func(db *DB) *DB {
		return db.Having(query, args...)
	})
}

func (c chainG[T]) Order(value interface{}) ChainInterface[T] {
	return c.with(func(db *DB) *DB {
		return db.Order(value)
	})

}

var (
	sqlLexer = lexer.Must(lexer.Regexp(`(\s+)` +
		`|(?P<Timeword>(?i)\b(?:YEAR|MONTH|DAY|HOUR|MINUTE|SECOND|TIMEZONE_HOUR|TIMEZONE_MINUTE)\b)` +

Try to find the good side. In general, if people are not being unfriendly, try to thank their effort and interest, even if you disagree with the main subject (discussion, PR), just thank them for being interested in the project, or for having dedicated some time to try to do something.

It's difficult to convey emotion in text, use emojis to help. 😅

    * You can also add [`Security` dependencies with `scopes`](../advanced/security/oauth2-scopes.md){.internal-link target=_blank}.

/// tip

Having `dependencies` in the `APIRouter` can be used, for example, to require authentication for a whole group of *path operations*. Even if the dependencies are not added individually to each one of them.

///

/// check