for _, v := range []byte(sql) {
			if v == '?' {
				if len(vars) > idx {
					newSQL.WriteString(vars[idx])
					idx++
					continue
				}
			}
			newSQL.WriteByte(v)
		}

		sql = newSQL.String()
	} else {
		sql = numericPlaceholder.ReplaceAllString(sql, "$$$1$$")

		sql = numericPlaceholderRe.ReplaceAllStringFunc(sql, func(v string) string {
			num := v[1 : len(v)-1]

/// tip | Dica

Você pode usar qualquer outra biblioteca de banco de dados SQL ou NoSQL que quiser (em alguns casos chamadas de <abbr title="Object Relational Mapper, um termo sofisticado para uma biblioteca onde algumas classes representam tabelas SQL e instâncias representam linhas nessas tabelas">"ORMs"</abbr>), o FastAPI não obriga você a usar nada. 😎

///

* `Field(primary_key=True)` tells SQLModel that the `id` is the **primary key** in the SQL database (you can learn more about SQL primary keys in the SQLModel docs).

    By having the type as `int | None`, SQLModel will know that this column should be an `INTEGER` in the SQL database and that it should be `NULLABLE`.

# SQL (关系型) 数据库

/// info

这些文档即将被更新。🎉

当前版本假设Pydantic v1和SQLAlchemy版本小于2。

新的文档将包括Pydantic v2以及 <a href="https://sqlmodel.tiangolo.com/" class="external-link" target="_blank">SQLModel</a>（也是基于SQLAlchemy），一旦SQLModel更新为为使用Pydantic v2。

///

**FastAPI**不需要你使用SQL(关系型)数据库。

但是您可以使用任何您想要的关系型数据库。

在这里，让我们看一个使用着[SQLAlchemy](https://www.sqlalchemy.org/)的示例。

您可以很容易地将其调整为任何SQLAlchemy支持的数据库，如：

* PostgreSQL
* MySQL

& 👆 🔜 💪 🔗 ⏮️ 👆 **FastAPI** 🈸, 👂 📊 ⚪️➡️ 🎰 💽:

<img src="/img/tutorial/sql-databases/image01.png">

## 🔗 ⏮️ 💽 🔗

🚥 👆 💚 🔬 🗄 💽 (📁) 🔗, ➡ FastAPI, ℹ 🚮 🎚, 🚮 🏓, 🏓, ⏺, 🔀 📊, ♒️. 👆 💪 ⚙️ <a href="https://sqlitebrowser.org/" class="external-link" target="_blank">💽 🖥 🗄</a>.

⚫️ 🔜 👀 💖 👉:

<img src="/img/tutorial/sql-databases/image02.png">

	sql = dryRunDB.Or("a = ? or b = ?", "a", "b").Unscoped().Find(&User{}).Statement.SQL.String()
	if !regexp.MustCompile(`WHERE a = .+ or b = .+$`).MatchString(sql) {
		t.Fatalf("invalid sql generated, got %v", sql)
	}

	sql = dryRunDB.Not("a = ? or b = ?", "a", "b").Unscoped().Find(&User{}).Statement.SQL.String()
	if !regexp.MustCompile(`WHERE NOT \(a = .+ or b = .+\)$`).MatchString(sql) {
		t.Fatalf("invalid sql generated, got %v", sql)
	}
}

					if e, ok := v.Exprs[0].(Expr); ok {
						sql := strings.ToUpper(e.SQL)
						wrapInParentheses = strings.Contains(sql, AndWithSpace) || strings.Contains(sql, OrWithSpace)
					}
				}
			case AndConditions:
				if len(v.Exprs) == 1 {
					if e, ok := v.Exprs[0].(Expr); ok {
						sql := strings.ToUpper(e.SQL)
						wrapInParentheses = strings.Contains(sql, AndWithSpace) || strings.Contains(sql, OrWithSpace)
					}
				}
			case Expr:

		}
		return sql.FromInt(v), nil
	case simdjson.TypeUint:
		v, err := iter.Int()
		if err != nil {
			// Can't fit into int, convert to float.
			v, err := iter.Float()
			return sql.FromFloat(v), err
		}
		return sql.FromInt(v), nil
	case simdjson.TypeBool:
		v, err := iter.Bool()
		if err != nil {
			return nil, err
		}
		return sql.FromBool(v), nil
	case simdjson.TypeNull:
		return sql.FromNull(), nil

//
// /////////////////////////////////////////////////////////////////////
func errExpressionTooLong(err error) *s3Error {
	return &s3Error{
		code:       "ExpressionTooLong",
		message:    "The SQL expression is too long: The maximum byte-length for the SQL expression is 256 KB.",
		statusCode: 400,
		cause:      err,
	}
}

func errColumnTooLong(err error) *s3Error {
	return &s3Error{
		code:       "ColumnTooLong",

		t.Errorf("Table with escape character, got %v", r.Statement.SQL.String())
	}

	r = dryDB.Table("user as u").Select("name").Find(&User{}).Statement
	if !regexp.MustCompile("SELECT .name. FROM user as u WHERE .u.\\..deleted_at. IS NULL").MatchString(r.Statement.SQL.String()) {
		t.Errorf("Table with escape character, got %v", r.Statement.SQL.String())
	}