SQL 语句大全实例教程

SQL（结构化查询语言）是一种强大的语言，用于与关系型数据库进行交互。掌握 SQL 语句至关重要，因为它使您可以高效地管理和操作数据。本文提供了一份 SQL 语句大全，พร้อมตัวอย่างเพื่อ帮助您入门。

SQL 语句大全实例教程

创建和删除数据库

Create database: CREATE DATABASE my_database; Drop database: DROP DATABASE my_database;

创建和删除表

Create table: CREATE TABLE my_table (id INT PRIMARY KEY, name VARCHAR(255)); Drop table: DROP TABLE my_table;

插入数据

Insert single row: INSERT INTO my_table (id, name) VALUES (1, 'John'); Insert multiple rows: INSERT INTO my_table (id, name) VALUES (2, 'Jane'), (3, 'Bob');

选择数据

Select all columns: SELECT FROM my_table; Select specific columns: SELECT id, name FROM my_table; Filter data: SELECT FROM my_table WHERE id > 2;

更新数据

Update single row: UPDATE my_table SET name = 'John Doe' WHERE id = 1; Update multiple rows: UPDATE my_table SET name = name || ' Doe' WHERE id > 2;

删除数据

Delete single row: DELETE FROM my_table WHERE id = 1; Delete multiple rows: DELETE FROM my_table WHERE id > 2;

其他常见语句

Alter table: ALTER TABLE my_table ADD COLUMN age INT; Join tables: SELECT FROM my_table t1 JOIN my_table t2 ON t1.id = t2.id; Group and aggregate: SELECT name, COUNT() AS count FROM my_table GROUP BY name;

实例教程

1. 创建数据库和表:

```sql CREATE DATABASE my_database; CREATE TABLE my_table (id INT PRIMARY KEY, name VARCHAR(255)); ```

2. 插入数据:

```sql INSERT INTO my_table (id, name) VALUES (1, 'John'), (2, 'Jane'); ```

3. 选择数据:

```sql SELECT FROM my_table; ```

4. 过滤数据:

```sql SELECT FROM my_table WHERE id > 1; ```

5. 更新数据:

```sql UPDATE my_table SET name = 'John Doe' WHERE id = 1; ```

6. 删除数据:

```sql DELETE FROM my_table WHERE id = 2; ```

7. 连接表:

```sql SELECT FROM my_table t1 JOIN my_table t2 ON t1.id = t2.id; ```

8. 分组和汇总:

```sql SELECT name, COUNT() AS count FROM my_table GROUP BY name; ```