摘要： 在写Bash脚本时，开始处要写上#!/bin/bash。 阅读全文

摘要： What is view? Virtual views are relations that are defined by a query over other relations. They are not stored in the database, but can be queried as if they existed. The view relation conceptually contains the tuples in the query result, but is not precomputed and stored. Instead, the database ... 阅读全文

摘要： Coffman et al. showed that four condition must hold for there to be a (resource) deadlock: 1. Mutual exclusion condition. Each resource is either currently assigned to exactly one process or is available. 2. Hold and wait condition. Processes currently holding resources that were granted earlier... 阅读全文