Writes of misaligned data structures, on the other hand, require the disk's firmware to first read two sectors, modify portions of both sectors, and then write two sectors.
The READ privilege is required to reference a global variable and the WRITE privilege is required to modify the value of a global variable.
READ权限用于引用全局变量,而WRITE权限用于修改全局变量的值。
3
In the example, the pttuser user has read and write access to the database (only from the hostname of the web server) and therefore can access and modify each table in it.