/where/ Recent content in WHERE on 老张开工了 Hugo zh-cn Wed, 05 Feb 2025 10:00:00 +0800 /posts/2025/02/query-and-filter/ Wed, 05 Feb 2025 10:00:00 +0800 /posts/2025/02/query-and-filter/ SELECT 基础 创建练习表并插入数据 -- 创建练习数据库 CREATE DATABASE practice; \c practice -- 创建员工表 CREATE TABLE employees ( id SERIAL PRIMARY KEY, name VARCHAR(50) NOT NULL, department VARCHAR(30), salary NUMERIC(10,2), hire_date DATE, is_active BOOLEAN DEFAULT true ); -- 插入测试数据 INSERT INTO employees (name, department, salary, hire_date, is_active) VALUES ('张三', '技术部', 15000, '2023-01-15', true), ('李四', '技术部', 18000, '2022-06-01', true), ('王五', '市场部', 12000, '2023-03-10', true), ('赵六', '市场部', 11000, '2024-01-20', true), ('钱七', '技术部', 22000, '2021-09-01', true), ('孙八', '人事部', 9000, '2024-07-15', true), ('周九', '人事部', 9500, '2023-11-01', true), ('吴十', '技术部', 16000, '2023-06-20', false), ('郑一', '市场部', 10000, '2024-09-01', true), ('陈二', '财务部', 13000, '2022-12-01', true); 基本 SELECT -- 查询所有列 SELECT * FROM employees; -- 查询指定列 SELECT name, salary FROM employees; -- 列别名 SELECT name AS 姓名, salary AS 工资 FROM employees; -- 列计算 SELECT name, salary, salary * 1.