# Security - First Steps { #security-first-steps }

Let's imagine that you have your **backend** API in some domain.

And you have a **frontend** in another domain or in a different path of the same domain (or in a mobile application).

And you want to have a way for the frontend to authenticate with the backend, using a **username** and **password**.

We can use **OAuth2** to build that with **FastAPI**.

Sebastián Ramírez <******@****.***> 1731896744 +0100

Sebastián Ramírez <******@****.***> 1731170360 +0100

Sebastián Ramírez <******@****.***> 1731896744 +0100

Sebastián Ramírez <******@****.***> 1731896744 +0100

Sebastián Ramírez <******@****.***> 1735583217 +0000

Sebastián Ramírez <******@****.***> 1731896744 +0100

		}

		got := user{}
		results := DB.First(&got, "id = ?", u1.ID)
		if results.Error != nil {
			t.Fatalf("errors happened on first: %v", results.Error)
		} else if results.RowsAffected != 1 {
			t.Fatalf("rows affected expects: %v, got %v", 1, results.RowsAffected)
		} else if got.ID != u1.ID {
			t.Fatalf("first expects: %v, got %v", u1, got)
		}

		results = DB.Select("id, name").Find(&got)

	if err := DB.Where("roles2 IS NULL AND roles3 = ?", "").First(&result, data.ID).Error; err != nil {
		t.Fatalf("failed to query data, got error %v", err)
	}

	AssertEqual(t, result, data)

	if err := DB.Model(&result).Update("roles", "").Error; err != nil {
		t.Fatalf("failed to update data's roles, got error %v", err)
	}

	if err := DB.First(&result, data.ID).Error; err != nil {

	DB.Create(&namedUser)

	var result NamedUser
	DB.First(&result, "name1 = @name OR name2 = @name OR name3 = @name", sql.Named("name", "jinzhu2"))

	AssertEqual(t, result, namedUser)

	var result2 NamedUser
	DB.Where("name1 = @name OR name2 = @name OR name3 = @name", sql.Named("name", "jinzhu2")).First(&result2)

	AssertEqual(t, result2, namedUser)

	var result3 NamedUser