+ (33.33 - MANY_VALUES_MEAN) * (33.33 - MANY_VALUES_MEAN)
          + (555.555 - MANY_VALUES_MEAN) * (555.555 - MANY_VALUES_MEAN)
          + (-2.2 - MANY_VALUES_MEAN) * (-2.2 - MANY_VALUES_MEAN);
  static final double MANY_VALUES_MAX = 555.555;
  static final double MANY_VALUES_MIN = -44.44;

  // Doubles which will overflow if summed:

const (
	HasOne    RelationshipType = "has_one"      // HasOneRel has one relationship
	HasMany   RelationshipType = "has_many"     // HasManyRel has many relationship
	BelongsTo RelationshipType = "belongs_to"   // BelongsToRel belongs to relationship
	Many2Many RelationshipType = "many_to_many" // Many2ManyRel many to many relationship
	has       RelationshipType = "has"
)

type Relationships struct {
	HasOne    []*Relationship

It is also commonly used for other applications that don't necessarily need a database, user management, or any of the many features that come pre-built in Django. Although many of these features can be added with plug-ins.

This decoupling of parts, and being a "microframework" that could be extended to cover exactly what is needed was a key feature that I wanted to keep.

In almost any framework handling the security becomes a rather complex subject quite quickly.

Many packages that simplify it a lot have to make many compromises with the data model, database, and available features. And some of these packages that simplify things too much actually have security flaws underneath.

---

**FastAPI** doesn't make any compromise with any database, data model or tool.

In many cases you might already know the answer for those questions. 🤓

If you are helping a lot of people with their questions, you will become an official [FastAPI Expert](fastapi-people.md#fastapi-experts){.internal-link target=_blank}. 🎉

One particular advantage that is not necessarily obvious is that you can **generate clients** (sometimes called <abbr title="Software Development Kits">**SDKs**</abbr> ) for your API, for many different **programming languages**.

## OpenAPI Client Generators

There are many tools to generate clients from **OpenAPI**.

 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* There can be **multiple processes** of the **same program** running at the same time.

If you check out the "task manager" or "system monitor" (or similar tools) in your operating system, you will be able to see many of those processes running.

	AssertEqual(t, err, gorm.ErrPrimaryKeyRequired)
	// has many
	err = DB.Model(&emptyUser).Association("Pets").Delete(&user1.Pets)
	AssertEqual(t, err, gorm.ErrPrimaryKeyRequired)
	// has one
	err = DB.Model(&emptyUser).Association("Account").Delete(&user1.Account)
	AssertEqual(t, err, gorm.ErrPrimaryKeyRequired)
	// many to many
	err = DB.Model(&emptyUser).Association("Languages").Delete(&user1.Languages)