SQL EXISTS语句使用实例：查询关联数据

查询所有存在订单的客户信息\n\n\nSELECT *\nFROM customers\nWHERE EXISTS (\n SELECT *\n FROM orders\n WHERE customers.customer_id = orders.customer_id\n);\n\n\n2. 查询存在未完成任务的员工信息\n\n\nSELECT *\nFROM employees\nWHERE EXISTS (\n SELECT *\n FROM tasks\n WHERE employees.employee_id = tasks.employee_id\n AND tasks.status <> 'completed'\n);\n\n\n3. 查询存在评论的电影信息\n\n\nSELECT *\nFROM movies\nWHERE EXISTS (\n SELECT *\n FROM reviews\n WHERE movies.movie_id = reviews.movie_id\n);\n