我认为此命令行没有任何意义，但是可以通过任何方式进行:

I don't think this command line does make a lot of sense, but any way:

NET START 列出所有正在运行的服务，此命令的输出发送到 FIND 工具，该工具在输入的字符串中搜索字符串"MSSQLSERVER"给定的.如果输入的任何行与搜索条件相匹配，则find将在屏幕上打印这些行，除非在这种情况下，将输入发送到空设备.这是一部分:> nul.

NET START lists all running services, the output of this command is sent to the FIND tool, which searches for the string "MSSQLSERVER" in the input it has been given. If any line of the input matches the search condition find prints these lines an the screen, unless in a case like this, where the input is send to the null device. This is the part : > nul.