# Testing a Database

You can study about databases, SQL, and SQLModel in the <a href="https://sqlmodel.tiangolo.com/" class="external-link" target="_blank">SQLModel docs</a>. 🤓

There's a mini <a href="https://sqlmodel.tiangolo.com/tutorial/fastapi/" class="external-link" target="_blank">tutorial on using SQLModel with FastAPI</a>. ✨

Sebastián Ramírez <******@****.***> 1585249793 +0100

Guilherme Rameh <******@****.***> 1729253044 -0300

    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`.

* `Field(index=True)` tells SQLModel that it should create a **SQL index** for this column, that would allow faster lookups in the database when reading data filtered by this column.

---> 100%
```

</div>

## ✍ 🇸🇲 🍕

➡️ 🔗 📁 `sql_app/database.py`.

### 🗄 🇸🇲 🍕

```Python hl_lines="1-3"
{!../../docs_src/sql_databases/sql_app/database.py!}
```

### ✍ 💽 📛 🇸🇲

```Python hl_lines="5-6"
{!../../docs_src/sql_databases/sql_app/database.py!}
```

👉 🖼, 👥 "🔗" 🗄 💽 (📂 📁 ⏮️ 🗄 💽).

📁 🔜 🔎 🎏 📁 📁 `sql_app.db`.

	Username           string    `json:"username"` // default: user running minio
	Password           string    `json:"password"` // default: no password
	Database           string    `json:"database"` // default: same as user
	QueueDir           string    `json:"queueDir"`
	QueueLimit         uint64    `json:"queueLimit"`
	MaxOpenConnections int       `json:"maxOpenConnections"`
}

pkg database/sql, const LevelDefault = 0
pkg database/sql, const LevelDefault IsolationLevel
pkg database/sql, const LevelLinearizable = 7
pkg database/sql, const LevelLinearizable IsolationLevel
pkg database/sql, const LevelReadCommitted = 2
pkg database/sql, const LevelReadCommitted IsolationLevel
pkg database/sql, const LevelReadUncommitted = 1
pkg database/sql, const LevelReadUncommitted IsolationLevel

import peewee

from .database import db


class User(peewee.Model):
    email = peewee.CharField(unique=True, index=True)
    hashed_password = peewee.CharField()
    is_active = peewee.BooleanField(default=True)

    class Meta:
        database = db


class Item(peewee.Model):
    title = peewee.CharField(index=True)
    description = peewee.CharField(index=True)
    owner = peewee.ForeignKeyField(User, backref="items")

	sqlserverDSN = "sqlserver://sa:LoremIpsum86@localhost:9930?database=master"
	tidbDSN      = "root:@tcp(localhost:9940)/test?charset=utf8&parseTime=True&loc=Local"
)

func init() {
	var err error
	if DB, err = OpenTestConnection(&gorm.Config{}); err != nil {
		log.Printf("failed to connect database, got error %v", err)
		os.Exit(1)
	} else {
		sqlDB, err := DB.DB()
		if err != nil {

---> 100%
```

</div>

## 创建 SQLAlchemy 部件

让我们转到文件`sql_app/database.py`。

### 导入 SQLAlchemy 部件

```Python hl_lines="1-3"
{!../../docs_src/sql_databases/sql_app/database.py!}
```

### 为 SQLAlchemy 定义数据库 URL地址

```Python hl_lines="5-6"
{!../../docs_src/sql_databases/sql_app/database.py!}
```

在这个例子中，我们正在“连接”到一个 SQLite 数据库（用 SQLite 数据库打开一个文件）。