SQL Delete 语句

DELETE 语句用于删除表中的记录。

## 语法

```sql
DELETE FROM table_name
WHERE some_column=some_value;
```

> 请注意 SQL DELETE 语句中的 WHERE 子句！WHERE 子句规定哪条记录或者哪些记录需要删除。如果您省略了 WHERE 子句，所有的记录都将被删除！

### 演示数据库

在本教程中，我们将使用众所周知的 Northwind 样本数据库。

下面是选自 "Customers" 表的数据：

| CustomerID | CustomerName | ContactName | Address | City | PostalCode | Country |
| --- | --- | --- | --- | --- | --- | --- |
| 1 | Alfreds Futterkiste | Maria Anders | Obere Str. 57 | Berlin | 12209 | Germany |
| 2 | Ana Trujillo Emparedados y helados | Ana Trujillo | Avda. de la Constitución 2222 | México D.F. | 05021 | Mexico |
| 3 | Antonio Moreno Taquería | Antonio Moreno | Mataderos 2312 | México D.F. | 05023 | Mexico |
| 4 | Around the Horn | Thomas Hardy | 120 Hanover Sq. | London | WA1 1DP | UK |
| 5 | Berglunds snabbköp | Christina Berglund | Berguvsvägen 8 | Luleå | S-958 22 | Sweden |

## 实例

假设我们要从 "Customers" 表中删除客户 "Alfreds Futterkiste"。

我们使用下面的 SQL 语句：

```sql
DELETE FROM Customers
WHERE CustomerName='Alfreds Futterkiste' AND ContactName='Maria Anders';
```

现在，"Customers" 表如下所示：

| CustomerID | CustomerName | ContactName | Address | City | PostalCode | Country |
| --- | --- | --- | --- | --- | --- | --- |
| 2 | Ana Trujillo Emparedados y helados | Ana Trujillo | Avda. de la Constitución 2222 | México D.F. | 05021 | Mexico |
| 3 | Antonio Moreno Taquería | Antonio Moreno | Mataderos 2312 | México D.F. | 05023 | Mexico |
| 4 | Around the Horn | Thomas Hardy | 120 Hanover Sq. | London | WA1 1DP | UK |
| 5 | Berglunds snabbköp | Christina Berglund | Berguvsvägen 8 | Luleå | S-958 22 | Sweden |

## 删除所有数据

您可以在不删除表的情况下，删除表中所有的行。这意味着表结构、属性、索引将保持不变：

```sql
DELETE FROM table_name;

DELETE * FROM table_name;
```

> **注释：**
>
> 在删除记录时要格外小心！因为您不能重来！