在PostgreSQL中,您可以使用ALTER TABLE
语句来向现有表添加新列。以下是几种常见的添加列的方法:
ALTER TABLE table_name ADD COLUMN column_name data_type [constraints];
ALTER TABLE employees ADD COLUMN email VARCHAR(100);
ALTER TABLE employees ADD COLUMN hire_date DATE DEFAULT CURRENT_DATE;
ALTER TABLE employees ADD COLUMN department VARCHAR(50) NOT NULL DEFAULT 'Unassigned';
ALTER TABLE employees
ADD COLUMN phone VARCHAR(20),
ADD COLUMN address TEXT;
ALTER TABLE products
ADD COLUMN discount_price NUMERIC(10,2)
CHECK (discount_price > 0 AND discount_price < price);
ALTER TABLE employees ADD COLUMN middle_name VARCHAR(50) AFTER first_name;
ALTER TABLE orders
ADD COLUMN total_price NUMERIC(10,2)
GENERATED ALWAYS AS (quantity * unit_price) STORED;
您需要根据具体需求选择合适的添加列方式。