20180522 Morning Lesson Records 15-mysql&linux

1.shell Script Execution If you use the current directory to execute, what do you think the command line is

./xxx.sh

2.A left join B, which table data is primary

A

3. What are grouped functions, syntax, and filtered SQL? What's the point of note?

GROUP BY
Having filter conditions
Note: Query columns are placed in group by, except functions

4. How is the child table understood?

A Word table is a temporary table formed by a query.

5. Table A, have you seen a and a table of their own join associations?

Yes

6. Inflate the table data what SQL do we use

Union

7.Linux which commands are r parameters

Rm-r
Cp-r

8.hdfs command execution, when the permissions can not be manipulated, how to do

Modify Permissions
Su-hadoop-c

9. Temporarily get root permission, command is what modify what file, that sentence is what

Sudo
/etc/sudoers Modify this file
Add Yonghu all= (root) nopasswd:all

10. Switch User what command, usually with what parameters

Su-

11. Can study questions sudo su be used together?

OK

12. If a user exists, is unable to login or SU cannot switch the past

/etc/passwd See this user last place
/sbin/nologin Change to/bin/bash

13. What is the command to view the port number?

Netstat-nlp|grep PID

14.Linux, for example, enter a command, say not found, ask how to do (expand the problem)

First see if the command is wrong and check the environment variable or find is not in the installation

20180522 Morning Lesson Records 15-mysql&linux