sql查询语句

我将为您提供一个SQL查询语句的示例,假设我们有一个名为"employees"的表,其中包含员工的信息,如姓名、年龄、部门和薪水,以下是一些常见的SQL查询语句:

sql查询语句
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1、选择所有列:

SELECT * FROM employees;

2、选择特定的列:

SELECT name, age, department FROM employees;

3、添加筛选条件:

SELECT * FROM employees WHERE age > 30;

4、对结果进行排序:

SELECT * FROM employees ORDER BY salary DESC;

5、使用聚合函数(如SUM、AVG、COUNT等):

SELECT SUM(salary) FROM employees;

6、分组数据:

SELECT department, COUNT(*) FROM employees GROUP BY department;

7、连接多个表:

SELECT employees.name, departments.department_name 
FROM employees 
INNER JOIN departments ON employees.department_id = departments.department_id;

8、创建新表:

CREATE TABLE new_table AS SELECT * FROM old_table;

9、更新表中的数据:

UPDATE employees SET salary = salary * 1.1 WHERE department = 'IT';

10、删除表中的数据:

DELETE FROM employees WHERE age < 25;

以上就是一些基本的SQL查询语句,希望对您有所帮助。